497

RULE 497 DOCUMENT

On behalf of Jacob Funds, Inc. (the “Company”), and pursuant to Rule 497(c) under the Securities Act of 1933, as amended (the “Securities Act”), the purpose of this filing is to submit an interactive data file in the manner provided by Rule 405 of Regulation S-T and General Instruction C.3.(g) of Form N-1A.  The interactive data file included as an exhibit to this filing relates to the form of prospectus filed with the Securities and Exchange Commission on behalf of the Company pursuant to Rule 497(c) under the Securities Act on October 9, 2012; such form of prospectus (accession number 0001450791-12-000231) is incorporated by reference into this Rule 497 Document.

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Jacob Wisdom Fund (Prospectus Summary) | Jacob Wisdom Fund

JACOB WISDOM FUND

Investment Objective

The Fund's investment objective is to maximize total investment return
consisting of a combination of income and capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the Fund.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees	Jacob Wisdom Fund Investor Class
Maximum Sales Charge (Load) Imposed on Purchases	none
Maximum Deferred Sales Charge (Load)	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	2.00%

Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		Jacob Wisdom Fund Investor Class
Advisory Fees		0.50%
Distribution and/or Service (12b-1) Fees		0.35%
Other Expenses		1.97%
Total Annual Fund Operating Expenses		2.82%
Fee Waiver	[1]	(0.50%)
Total Annual Fund Operating Expenses After Fee Waiver		2.32%

Example:

This example is intended to help you compare the cost of investing in the Fund
with the cost of investing in other mutual funds. The Example assumes that you
invest $10,000 in the Fund over the time periods indicated and then redeem all
of your shares at the end of those periods. The Example also assumes that your
investment has a 5% return each year and that the Fund's operating expenses
remain the same.

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Jacob Wisdom Fund Investor Class	235	827	1,445	3,111

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual fund operating expenses or in the example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 13.60%
of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objective by investing primarily in
equity securities of U.S. companies of any size. The Fund may gain exposure
to foreign markets through the global operations of U.S. companies, or through
direct investment in foreign companies. The Adviser will not invest more than
25% of the Fund's net assets directly in foreign companies. The Fund may, to a
lesser extent, invest in investment grade fixed income or debt securities to
seek income.

The Fund invests in securities of companies that the Adviser believes have the
greatest potential for capital appreciation and income. The Adviser's overall
stock selections are based on an assessment of a company's fundamental prospects.
Specifically, the Adviser uses fundamental analysis to assess the quality, growth
potential, financial strength and overall value of a company. While trying to
maximize the capital appreciation potential of the Fund's portfolio of investments,
the Adviser also seeks to obtain securities for the Fund that are selling at
reasonable prices.

The Fund maintains a diversified portfolio of investments consisting primarily
of common stocks, and may also invest in other equity securities such as
preferred stocks, securities convertible or exchangeable into common stock,
rights, warrants or real estate investment trusts (REITs). Equity securities
generally represent an ownership interest in a company and their value is based
on the success of the company's business, any income paid to shareholders, the
value of the company's assets, general market conditions and investor demand. The
Fund may also purchase depositary receipts, which are certificates normally issued
by U.S. banks that evidence the ownership of shares of a foreign company.

The Fund generally seeks to purchase securities as long-term investments, but
when circumstances warrant, securities may be sold without regard to the length
of time they have been held to reduce risk or volatility or to respond to
changing fundamental information.

The Fund intends to hold some cash, short-term debt obligations, government
securities or other high-quality investments for reserves to cover redemptions
and unanticipated expenses, to seek income, or to maintain liquidity while
seeking appropriate investments.

Principal Risks

Investing in a mutual fund has inherent risks, which could cause you to lose
money. The principal risks of investing in the Fund, and the circumstances that
could adversely affect the Fund's net asset value and total return, are listed
below.

·  Market Risk: Even when the stock market in general is rising, the stocks      
   selected by the Adviser may decline. Prices of common stocks of even the best
   managed, most profitable corporations are subject to market risk, which means
   their stock prices can decline. In addition, swings in investor psychology or
   significant trading by large institutional investors can result in price      
   fluctuations. The Adviser may not be able to sell stocks at an optimal time
   or price.                                                                        
  
·  Smaller Capitalized Company Risk: Investments in smaller capitalized companies
   may involve greater risks, as these companies may not have the management     
   experience, financial resources, product diversification and competitive      
   strengths of larger companies.                                                

·  Convertible Securities Risk: The market value of convertible securities tends
   to decline as interest rates increase and, conversely, to increase as interest
   rates decline. In addition, convertible securities generally offer lower      
   interest or dividend yields than non-convertible securities of similar        
   quality.                                                                      
  
·  Fixed Income Risk: Yields and principal values of fixed income securities     
   (bonds) will fluctuate. Generally, values of fixed income securities change   
   inversely with interest rates. As interest rates go up, the value of debt     
   securities tends to go down. As a result, to the extent the Fund holds fixed  
   income investments, the value of the Fund may go down. The issuers of         
   instruments in which the Fund invests may be unable to meet interest and/or   
   principal payments. An issuer's securities may decrease in value if its       
   financial strength weakens, which may reduce its credit rating and possibly   
   its ability to meet its contractual obligations.                              
  
·  Foreign Risk: The risks of investing in foreign companies can increase the    
   potential for losses in the Fund and may include currency fluctuations,       
   political and economic instability, less government regulation, less publicly
   available information, limited trading markets, differences in financial      
   reporting standards and less stringent regulation of securities markets.
   Foreign securities markets generally have less volume than U.S. securities
   exchanges and securities of some foreign companies are less liquid and more
   volatile than securities of comparable U.S. companies. Additional risks
   include future political and economic developments, the possibility that
   a foreign jurisdiction might impose or increase withholding taxes on income   
   payable with respect to foreign securities, the possible seizure,nationalization
   or expropriation of the foreign issuer or foreign deposits (in which the Fund
   could lose its entire investment in a certain market) and the possible adoption
   of foreign governmental restrictions such as exchange controls.                                                                     

·  Real Estate Investment Trust Risk: Investments in real estate related         
   instruments may be affected by economic, legal, cultural, environmental or    
   technological factors that affect property values, rents or occupancies of    
   real estate related to the Fund's holdings. The performance of REITs depends  
   on how well the REIT manages the properties it owns.

Performance Information

The performance information that follows gives some indication of the risks of
investing in the Fund. The bar chart shows the Fund's performance from year to
year, and the table compares the Fund's average annual returns with those of a
broad measure of market performance. Please note that the Fund's past performance
(before and after taxes) is not necessarily an indication of how the Fund will
perform in the future.

Annual Total Returns as of December 31, 2011 (Investor Class)

As of September 30, 2012, the Fund's year to date return was 14.40%.

Best Quarter       Q1     2012      9.56%
Worst Quarter      Q3     2011     -9.08%

Average Annual Total Returns as of December 31, 2011

Average Annual Total Returns Jacob Wisdom Fund	Label	1 Year	Since Inception
Investor Class	Return Before Taxes	3.59%	7.52%
Investor Class After Taxes on Distributions	Return After Taxes on Distributions	3.22%	7.31%
Investor Class After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	2.33%	6.32%
S&P® 500 Index	S&P® 500 Index (reflects no deduction for fees, expenses or taxes)	2.11%	8.42%

The performance information shown is for the period from December 1, 2009 to
December 31, 2011. The performance information shown for the period from
December 1, 2009, to February 17, 2010, is that of the Fund's predecessor, the
Wisdom Fund. The Adviser took over management of the Wisdom Fund on December 1,
2009, and the Wisdom Fund was reorganized into the Jacob Wisdom Fund on February
18, 2010.

After-tax returns are calculated using the historical highest individual federal
marginal income tax rates and do not reflect the impact of state and local
taxes. Actual after-tax returns depend on an investor's tax situation and may
differ from those shown. After-tax returns shown are not relevant to investors
who hold their Fund shares through tax-deferred arrangements such as 401(k)
plans or individual retirement accounts. The return after taxes on distribution
and sale of fund shares may be higher than the return before taxes because the
method of calculation assumes generally that you can use the short-term capital
loss realized upon the sale of fund shares to offset income of the same tax
character from other sources thereby reducing the amount of tax you otherwise
might owe.

[1] Jacob Asset Management of New York LLC, the Fund's investment adviser (the "Adviser"), has contractually agreed , through at least January 2, 2014, to waive up to 100% of its advisory fees, to the extent that the Total Annual Fund Operating Expenses (excluding any taxes, interest, brokerage fees, and extraordinary expenses) would exceed 1.95% of average daily net assets. This fee waiver agreement does not extend to indirect expenses of any acquired funds. Pursuant to this fee waiver agreement, the Adviser is entitled to recoup any fees that it waived for a period of three years following such fee waivers to the extent that such recoupment will not cause the Fund's expenses to exceed 1.95%. Please note that the maximum waiver is 0.50%, which means that the Fund's overall expenses could exceed 1.95%, as is the case above. This waiver agreement may only be terminated by the Board.

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Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Oct. 01, 2012
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	JACOB INTERNET FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Objectives
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's primary investment objective is long-term growth of capital.
Objective, Secondary [Text Block]	rr_ObjectiveSecondaryTextBlock	Current income is a secondary objective.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 52.39% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	52.39%
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund over the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its investment objectives by investing, under normal circumstances, at least 80% of its assets in securities of Internet companies and companies in Internet-related industries. The Fund primarily invests in common stocks and securities convertible into common stocks, but may invest up to 35% in fixed income or debt securities. The Internet is a collection of connected computers that allows commercial and professional organizations, educational institutions, government agencies, and consumers to communicate electronically, access and share information, and conduct business around the world. The Adviser selects investments in companies that derive a substantial portion of their revenue from Internet or Internet-related businesses or those that are aggressively developing and expanding their Internet and Internet-related business operations. The Adviser believes that the Internet offers unique investment opportunities because of its ever-growing popularity among business and personal users alike. Many Internet companies are newer and have small to medium market capitalizations. The Fund invests in companies that emphasize research and development with respect to proprietary products and services for Internet users and businesses, because the Adviser believes that these stocks have the greatest potential to rise in value. The Adviser's overall stock selections are based on an assessment of a company's fundamental prospects. The Fund generally seeks to purchase securities as long-term investments, but when circumstances warrant, securities may be sold without regard to the length of time they have been held to reduce risk or volatility or to respond to changing fundamental information. The Fund may invest without limitation in foreign securities, including securities of emerging market countries, so that the Fund has the flexibility to take full advantage of investment opportunities in Internet companies and companies in Internet-related industries. The Fund intends to hold some cash, short-term debt obligations, government securities or other high-quality investments for reserves to cover redemptions and unanticipated expenses, to seek income, or to maintain liquidity while seeking appropriate investments.
Strategy Portfolio Concentration [Text]	rr_StrategyPortfolioConcentration	The Fund seeks to achieve its investment objectives by investing, under normal circumstances, at least 80% of its assets in securities of Internet companies and companies in Internet-related industries.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Investing in a mutual fund has inherent risks, which could cause you to lose money. The principal risks of investing in the Fund, and the circumstances that could adversely affect the Fund's net asset value and total return, are listed below. ·  Market Risk: Even when the stock market in general is rising, the stocks          selected by the Adviser may decline. Prices of common stocks of even the best    managed, most profitable corporations are subject to market risk, which means    their stock prices can decline. In addition, swings in investor psychology or    significant trading by large institutional investors can result in price          fluctuations. The Adviser may not be able to sell stocks at an optimal time    or price.                                                                            ·  Internet Company Risk: Many Internet-related companies have incurred large        losses since their inception and will continue to incur large losses in the       hope of capturing market share and generating future revenues. Accordingly,       many such companies expect to incur significant operating losses for the          foreseeable future, and may never be profitable.                                  ·  Computer/Internet Technology Risk: Companies in the rapidly changing field of    computer/Internet technology face special risks. For example, their products      or services may not prove commercially successful or may become obsolete          quickly. The value of the Fund's shares may be susceptible to factors             affecting the computer/Internet technology area and to greater risk and market    fluctuation than an investment in a fund that invests in a broader range of       portfolio securities not concentrated in any particular area or industry.    The computer/Internet technology area may be subject to greater governmental          regulation than many other areas and changes in governmental policies and the    need for regulatory approvals may have a material adverse effect on these         areas. Additionally, companies in these areas may be subject to risks of          developing technologies, competitive pressures and other factors and are          dependent upon consumer and business acceptance as new technologies evolve.    ·  Smaller Capitalized or Unseasoned Company Risk: The Adviser believes that         smaller capitalized or unseasoned companies generally have greater earnings       and sales growth potential than larger capitalized companies. However,            investments in smaller capitalized or unseasoned companies may involve greater    risks, in part because they have limited product lines, markets and financial    or managerial resources. In addition, less frequently-traded securities may be    subject to more abrupt price movements than securities of larger capitalized      companies.                                                                        ·  Convertible Securities Risk: The market value of convertible securities tends    to decline as interest rates increase and, conversely, to increase as interest    rates decline. In addition, convertible securities generally offer lower          interest or dividend yields than non-convertible securities of similar            quality.                                                                          ·  Foreign and Emerging Market Risk: The risks of investing in foreign companies,    including those located in emerging market countries, can increase the potential    for losses in the Fund and may include currency fluctuations, political and    economic instability, less government regulation, less publicly available    information, limited trading markets, differences in financial reporting standards    and less stringent regulation of securities markets. Foreign securities markets    generally have less volume than U.S. securities exchanges and securities of some    foreign companies are less liquid and more volatile than securities of comparable    U.S. companies. Additional risks include future political and economic developments,    the possibility that a foreign jurisdiction might impose or increase withholding    taxes on income payable with respect to foreign securities, the possible seizure,                 nationalization or expropriation of the foreign issuer or foreign deposits (in    which the Fund could lose its entire investment in a certain market) and the      possible adoption of foreign governmental restrictions such as exchange           controls.                                                                       ·  Fixed Income Risk: Yields and principal values of fixed income securities         (bonds) will fluctuate. Generally, values of fixed income securities change       inversely with interest rates. As interest rates go up, the value of debt         securities tends to go down. As a result, to the extent the Fund holds fixed      income investments, the value of the Fund may go down.
Risk Lose Money [Text]	rr_RiskLoseMoney	Investing in a mutual fund has inherent risks, which could cause you to lose money.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The performance information that follows gives some indication of the risks of investing in the Fund. The bar chart shows the Fund's performance from year to year, and the table compares the Fund's average annual returns with those of two broad measures of market performance and an index of Internet stocks. Please note that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The performance information that follows gives some indication of the risks of investing in the Fund.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Please note that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns as of December 31, 2011 (Investor Class)
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	As of September 30, 2012, the Fund's year to date return was 16.24%. Best Quarter     Q4   2002   60.00% Worst Quarter    Q3   2001  -51.20%
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	reflects no deduction for fees, expenses or taxes
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.
Performance Table Explanation after Tax Higher	rr_PerformanceTableExplanationAfterTaxHigher	The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns as of December 31, 2011
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund | S&P® 500 Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	S&P® 500 Index (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	2.11%
5 Years	rr_AverageAnnualReturnYear05	(0.25%)
10 Years	rr_AverageAnnualReturnYear10	2.92%
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund | NASDAQ Composite Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	NASDAQ Composite Index (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(0.79%)
5 Years	rr_AverageAnnualReturnYear05	2.50%
10 Years	rr_AverageAnnualReturnYear10	3.74%
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund | Bloomberg U.S. Internet Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Bloomberg U.S. Internet Index (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(5.87%)
5 Years	rr_AverageAnnualReturnYear05	1.71%
10 Years	rr_AverageAnnualReturnYear10	1.33%
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	(2.00%)
Advisory Fees	rr_ManagementFeesOverAssets	1.25%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.35%
Other Expenses	rr_OtherExpensesOverAssets	1.09%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.69%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	272
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	835
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,425
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	3,022
Annual Return 2002	rr_AnnualReturn2002	(13.04%)
Annual Return 2003	rr_AnnualReturn2003	101.25%
Annual Return 2004	rr_AnnualReturn2004	32.30%
Annual Return 2005	rr_AnnualReturn2005	10.80%
Annual Return 2006	rr_AnnualReturn2006	16.24%
Annual Return 2007	rr_AnnualReturn2007	(0.80%)
Annual Return 2008	rr_AnnualReturn2008	(51.15%)
Annual Return 2009	rr_AnnualReturn2009	71.88%
Annual Return 2010	rr_AnnualReturn2010	35.45%
Annual Return 2011	rr_AnnualReturn2011	(9.06%)
Year to Date Return, Label	rr_YearToDateReturnLabel	year to date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	16.24%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2002
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	60.00%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2001
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(51.20%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(9.06%)
5 Years	rr_AverageAnnualReturnYear05	0.52%
10 Years	rr_AverageAnnualReturnYear10	11.83%
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund | Investor Class | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(9.06%)
5 Years	rr_AverageAnnualReturnYear05	0.43%
10 Years	rr_AverageAnnualReturnYear10	11.74%
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund | Investor Class | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(5.89%)
5 Years	rr_AverageAnnualReturnYear05	0.42%
10 Years	rr_AverageAnnualReturnYear10	10.61%

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Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund

JACOB INTERNET FUND

Investment Objectives

The Fund's primary investment objective is long-term growth of capital.

Current income is a secondary objective.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the Fund.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees	Jacob Internet Fund Investor Class
Maximum Sales Charge (Load) Imposed on Purchases	none
Maximum Deferred Sales Charge (Load)	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	2.00%

Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Jacob Internet Fund Investor Class
Advisory Fees	1.25%
Distribution and/or Service (12b-1) Fees	0.35%
Other Expenses	1.09%
Total Annual Fund Operating Expenses	2.69%

Example:

This example is intended to help you compare the cost of investing in the Fund
with the cost of investing in other mutual funds. The Example assumes that you
invest $10,000 in the Fund over the time periods indicated and then redeem all
of your shares at the end of those periods. The Example also assumes that your
investment has a 5% return each year and that the Fund's operating expenses
remain the same.

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Jacob Internet Fund Investor Class	272	835	1,425	3,022

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual fund operating expenses or in the example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 52.39%
of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objectives by investing, under normal
circumstances, at least 80% of its assets in securities of Internet companies
and companies in Internet-related industries. The Fund primarily invests in
common stocks and securities convertible into common stocks, but may invest
up to 35% in fixed income or debt securities. The Internet is a collection
of connected computers that allows commercial and professional organizations,
educational institutions, government agencies, and consumers to communicate
electronically, access and share information, and conduct business around the
world. The Adviser selects investments in companies that derive a substantial
portion of their revenue from Internet or Internet-related businesses or
those that are aggressively developing and expanding their Internet and
Internet-related business operations. The Adviser believes that the Internet
offers unique investment opportunities because of its ever-growing popularity
among business and personal users alike. Many Internet companies are newer and
have small to medium market capitalizations.

The Fund invests in companies that emphasize research and development with
respect to proprietary products and services for Internet users and businesses,
because the Adviser believes that these stocks have the greatest potential to
rise in value. The Adviser's overall stock selections are based on an assessment
of a company's fundamental prospects. The Fund generally seeks to purchase
securities as long-term investments, but when circumstances warrant, securities
may be sold without regard to the length of time they have been held to reduce
risk or volatility or to respond to changing fundamental information. The Fund
may invest without limitation in foreign securities, including securities of
emerging market countries, so that the Fund has the flexibility to take full
advantage of investment opportunities in Internet companies and companies in
Internet-related industries.

The Fund intends to hold some cash, short-term debt obligations, government
securities or other high-quality investments for reserves to cover redemptions
and unanticipated expenses, to seek income, or to maintain liquidity while
seeking appropriate investments.

Principal Risks

Investing in a mutual fund has inherent risks, which could cause you to lose
money. The principal risks of investing in the Fund, and the circumstances that
could adversely affect the Fund's net asset value and total return, are listed
below.

·  Market Risk: Even when the stock market in general is rising, the stocks      
   selected by the Adviser may decline. Prices of common stocks of even the best
   managed, most profitable corporations are subject to market risk, which means
   their stock prices can decline. In addition, swings in investor psychology or
   significant trading by large institutional investors can result in price      
   fluctuations. The Adviser may not be able to sell stocks at an optimal time
   or price.                                                                        
  
·  Internet Company Risk: Many Internet-related companies have incurred large    
   losses since their inception and will continue to incur large losses in the   
   hope of capturing market share and generating future revenues. Accordingly,   
   many such companies expect to incur significant operating losses for the      
   foreseeable future, and may never be profitable.                              
  
·  Computer/Internet Technology Risk: Companies in the rapidly changing field of
   computer/Internet technology face special risks. For example, their products  
   or services may not prove commercially successful or may become obsolete      
   quickly. The value of the Fund's shares may be susceptible to factors         
   affecting the computer/Internet technology area and to greater risk and market
   fluctuation than an investment in a fund that invests in a broader range of   
   portfolio securities not concentrated in any particular area or industry.
   The computer/Internet technology area may be subject to greater governmental      
   regulation than many other areas and changes in governmental policies and the
   need for regulatory approvals may have a material adverse effect on these     
   areas. Additionally, companies in these areas may be subject to risks of      
   developing technologies, competitive pressures and other factors and are      
   dependent upon consumer and business acceptance as new technologies evolve.   

·  Smaller Capitalized or Unseasoned Company Risk: The Adviser believes that     
   smaller capitalized or unseasoned companies generally have greater earnings   
   and sales growth potential than larger capitalized companies. However,        
   investments in smaller capitalized or unseasoned companies may involve greater
   risks, in part because they have limited product lines, markets and financial
   or managerial resources. In addition, less frequently-traded securities may be
   subject to more abrupt price movements than securities of larger capitalized  
   companies.                                                                    
  
·  Convertible Securities Risk: The market value of convertible securities tends
   to decline as interest rates increase and, conversely, to increase as interest
   rates decline. In addition, convertible securities generally offer lower      
   interest or dividend yields than non-convertible securities of similar        
   quality.                                                                      
  
·  Foreign and Emerging Market Risk: The risks of investing in foreign companies,
   including those located in emerging market countries, can increase the potential
   for losses in the Fund and may include currency fluctuations, political and
   economic instability, less government regulation, less publicly available
   information, limited trading markets, differences in financial reporting standards
   and less stringent regulation of securities markets. Foreign securities markets
   generally have less volume than U.S. securities exchanges and securities of some
   foreign companies are less liquid and more volatile than securities of comparable
   U.S. companies. Additional risks include future political and economic developments,
   the possibility that a foreign jurisdiction might impose or increase withholding
   taxes on income payable with respect to foreign securities, the possible seizure,             
   nationalization or expropriation of the foreign issuer or foreign deposits (in
   which the Fund could lose its entire investment in a certain market) and the  
   possible adoption of foreign governmental restrictions such as exchange       
   controls.  
                                                                   
·  Fixed Income Risk: Yields and principal values of fixed income securities     
   (bonds) will fluctuate. Generally, values of fixed income securities change   
   inversely with interest rates. As interest rates go up, the value of debt     
   securities tends to go down. As a result, to the extent the Fund holds fixed  
   income investments, the value of the Fund may go down.

Performance Information

The performance information that follows gives some indication of the risks of
investing in the Fund. The bar chart shows the Fund's performance from year to
year, and the table compares the Fund's average annual returns with those of two
broad measures of market performance and an index of Internet stocks. Please
note that the Fund's past performance (before and after taxes) is not necessarily
an indication of how the Fund will perform in the future.

Annual Total Returns as of December 31, 2011 (Investor Class)

As of September 30, 2012, the Fund's year to date return was 16.24%.

Best Quarter     Q4   2002   60.00%
Worst Quarter    Q3   2001  -51.20%

Average Annual Total Returns as of December 31, 2011

Average Annual Total Returns Jacob Internet Fund	Label	1 Year	5 Years	10 Years
Investor Class	Return Before Taxes	(9.06%)	0.52%	11.83%
Investor Class After Taxes on Distributions	Return After Taxes on Distributions	(9.06%)	0.43%	11.74%
Investor Class After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	(5.89%)	0.42%	10.61%
S&P® 500 Index	S&P® 500 Index (reflects no deduction for fees, expenses or taxes)	2.11%	(0.25%)	2.92%
NASDAQ Composite Index	NASDAQ Composite Index (reflects no deduction for fees, expenses or taxes)	(0.79%)	2.50%	3.74%
Bloomberg U.S. Internet Index	Bloomberg U.S. Internet Index (reflects no deduction for fees, expenses or taxes)	(5.87%)	1.71%	1.33%

After-tax returns are calculated using the historical highest individual federal
marginal income tax rates and do not reflect the impact of state and local
taxes. Actual after-tax returns depend on an investor's tax situation and may
differ from those shown. After-tax returns shown are not relevant to investors
who hold their Fund shares through tax-deferred arrangements such as 401(k)
plans or individual retirement accounts. The return after taxes on distribution
and sale of fund shares may be higher than the return before taxes because the
method of calculation assumes generally that you can use the short-term capital
loss realized upon the sale of fund shares to offset income of the same tax
character from other sources thereby reducing the amount of tax you otherwise
might owe.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Oct. 01, 2012
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	JACOB SMALL CAP GROWTH FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is long-term growth of capital.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 102.80% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	102.80%
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund over the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its assets in small capitalization companies. Small capitalization companies are defined as those companies with market capitalizations (share price multiplied by number of shares outstanding) within the capitalization range of the Russell 2000® Growth Index at the time of purchase.  As of August 31, 2012, the market capitalization of the largest company in the Russell 2000® Growth Index was approximately $4.621 billion, and the weighted average and median market capitalizations of the Russell 2000® Growth Index were approximately $1.431 billion and $584 million, respectively. The Fund maintains a diversified portfolio of investments consisting primarily of common stocks. The Fund may also invest in other equity securities such as preferred stocks, securities convertible or exchangeable into common stocks, rights, warrants, or real estate investment trusts. The Adviser expects to select investments for the Fund in companies that are broadly diversified over various industry groups. The Adviser manages the Fund's portfolio in an aggressive growth style. The Adviser believes that investments in small capitalization companies can have greater earnings and sales growth potential than larger capitalized companies and can offer substantial opportunities for long-term growth of capital. The Adviser's overall stock selections are based on its qualitative and quantitative assessment of a company's fundamental prospects and whether it has an above-average potential for long-term growth of capital. The Adviser expects to invest the Fund's net assets primarily in U.S. companies, but may gain exposure to foreign markets through the global operations of U.S. companies, by purchasing depositary receipts or securities of foreign companies traded on U.S. exchanges, or through direct investment in foreign companies. The Adviser will not invest more than 25% of the Fund's net assets directly in foreign companies. The Fund intends to hold some cash, short-term debt obligations, government securities or other high-quality investments for reserves to cover redemptions and unanticipated expenses, or to maintain liquidity while seeking appropriate investments.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Investing in a mutual fund has inherent risks, which could cause you to lose money. The principal risks of investing in the Fund, and the circumstances that could adversely affect the Fund's net asset value and total return, are listed below. ·  Market Risk: The value of the Fund's shares and the securities held by the        Fund can each decline in value. Even when the stock market in general is          rising, the stocks selected by the Adviser may decline. Prices of common          stocks of even the best managed, most profitable corporations are subject to      market risk, which means their stock prices can decline. In addition, swings      in investor psychology or significant trading by large institutional investors    can result in price fluctuations.                                                 ·  Smaller Capitalized Company Risk: Investments in small capitalization             companies may involve greater risks, as these companies tend to have limited      product lines, markets and financial or managerial resources. Small cap stocks    often also have a more limited trading market, such that the Adviser may not      be able to sell stocks at an optimal time or price. In addition, less             frequently-traded securities may be subject to more abrupt price movements        than securities of larger capitalized companies.                                  ·  Growth Companies Risk. Growth companies are expected to increase their            earnings at a certain rate. When these expectations are not met, the prices of    these stocks may go down, even if earnings showed an absolute increase. Growth    company stocks also typically lack the dividend yield that can cushion stock      prices in market downturns. Different investment styles tend to shift in and      out of favor, depending on market conditions and investor sentiment. The          Fund's growth style may cause the Fund to underperform funds that have a          broader investment style.                                                      ·  Foreign and Emerging Market Risk: The risks of investing in foreign companies,    including those located in emerging market countries, can increase the potential    for losses in the Fund and may include currency fluctuations, political and    economic instability, less government regulation, less publicly available    information, limited trading markets, differences in financial reporting standards    and less stringent regulation of securities markets. Foreign securities markets    generally have less volume than U.S. securities exchanges and securities of some    foreign companies are less liquid and more volatile than securities of comparable    U.S. companies. Additional risks include future political and economic developments,    the possibility that a foreign jurisdiction might impose or increase withholding    taxes on income payable with respect to foreign securities, the possible seizure,                 nationalization or expropriation of the foreign issuer or foreign deposits (in    which the Fund could lose its entire investment in a certain market) and the      possible adoption of foreign governmental restrictions such as exchange           controls.
Risk Lose Money [Text]	rr_RiskLoseMoney	Investing in a mutual fund has inherent risks, which could cause you to lose money.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The performance information that follows gives some indication of the risks of investing in the Fund. The bar chart shows the Fund's performance for the last calendar year, and the table compares the Fund's average annual returns with those of a broad measure of market performance. Please note that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Performance information is not presented for Institutional Class shares of the Fund because the Fund had not issued Institutional Class shares as of the date of this Prospectus.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The performance information that follows gives some indication of the risks of investing in the Fund.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Please note that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns as of December 31, 2011 (Investor Class)
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	As of September 30, 2012, the Fund's year to date return was 14.52%. Best Quarter       Q4     2010      22.86% Worst Quarter      Q3     2011     -27.18%
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	reflects no deduction for fees, expenses or taxes
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.
Performance Table Explanation after Tax Higher	rr_PerformanceTableExplanationAfterTaxHigher	The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns as of December 31, 2011
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Russell 2000® Growth Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(2.91%)
Since Inception	rr_AverageAnnualReturnSinceInception	14.51%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	(2.00%)
Advisory Fees	rr_ManagementFeesOverAssets	0.90%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.35%
Other Expenses	rr_OtherExpensesOverAssets	1.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.43%
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.18%)	[1]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	2.25%	[2]
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-01-02
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	228
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	740
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,279
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,753
Annual Return 2011	rr_AnnualReturn2011	(13.93%)
Year to Date Return, Label	rr_YearToDateReturnLabel	year to date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	14.52%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2010
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	22.86%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(27.18%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(13.93%)
Since Inception	rr_AverageAnnualReturnSinceInception	10.05%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Investor Class | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(15.34%)
Since Inception	rr_AverageAnnualReturnSinceInception	9.10%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Investor Class | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(9.05%)
Since Inception	rr_AverageAnnualReturnSinceInception	8.05%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Institutional Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	none
Advisory Fees	rr_ManagementFeesOverAssets	0.90%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	1.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.08%
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.13%)	[1]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.95%	[2]
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-01-02
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	198
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	639
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,107
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,400
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01
Since Inception	rr_AverageAnnualReturnSinceInception
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010

[1] Jacob Asset Management of New York LLC, the Fund's investment adviser (the "Adviser"), has contractually agreed, through at least January 2, 2014, to waive up to 100% of its advisory fees to the extent that the Total Annual Fund Operating Expenses (excluding any taxes, interest, brokerage fees, and extraordinary expenses) exceed 2.25% or 1.95% for Investor Class shares and Institutional Class shares, respectively, of each class' average daily net assets. This fee waiver agreement does not extend to indirect expenses of any acquired funds. Pursuant to this fee waiver agreement, the Adviser is entitled to recoup any fees that it waived for a period of three years following such fee waivers to the extent that such recoupment will not cause the Fund to exceed any applicable expense limitation that was in place for the Fund when the fees were waived. Please note that the maximum waiver is 0.90%, which means that the Fund's overall expenses could exceed 2.25% for Investor Class shares or 1.95% for Institutional Class shares. This waiver agreement may only be terminated by the Board. Please also note that this fee waiver agreement is contingent upon the closing of the reorganization of the Jacob Small Cap Growth Fund II (formerly PineBridge US Small Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. Otherwise the fee waiver agreement currently in place for Investor Class shares of the Fund (which operates as described above with fees waived if expenses exceed 2.45%) will apply through at least January 2, 2014.

[2] Please note that the percentage of Annual Fund Operating Expenses shown is based on estimated amounts and on the amount of assets expected to transfer into the Fund as a result of the reorganization of the Jacob Small Cap Growth Fund II (formerly PineBridge US Small Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. If the Fund's average annual net assets during the current fiscal year are lower, the Fund's expense ratio would be higher than that shown above.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
Document Type	dei_DocumentType	Other
Document Period End Date	dei_DocumentPeriodEndDate	Oct. 01, 2012
Registrant Name	dei_EntityRegistrantName	Jacob Funds Inc.
Central Index Key	dei_EntityCentralIndexKey	0001090372
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Oct. 09, 2012
Document Effective Date	dei_DocumentEffectiveDate	Oct. 09, 2012
Jacob Internet Fund (Prospectus Summary) | Jacob Internet Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	JAMFX
Jacob Wisdom Fund (Prospectus Summary) | Jacob Wisdom Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	JWSFX
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	JSCGX
Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro Cap Growth Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	N/A

XML

Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro Cap Growth Fund

JACOB MICRO CAP GROWTH FUND

Investment Objective

The Fund's investment objective is long-term growth of capital.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the Fund.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees Jacob Micro Cap Growth Fund	Investor Class	Institutional Class
Maximum Sales Charge (Load) Imposed on Purchases	none	none
Maximum Deferred Sales Charge (Load)	none	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	none	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	2.00%	none

Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)

Annual Fund Operating Expenses Jacob Micro Cap Growth Fund		Investor Class	Institutional Class
Advisory Fees		1.20%	1.20%
Distribution and/or Service (12b-1) Fees		0.35%	none
Other Expenses		0.64%	0.64%
Total Annual Fund Operating Expenses	[1]	2.19%	1.84%

Example:

This example is intended to help you compare the cost of investing in the Fund
with the cost of investing in other mutual funds. The Example assumes that you
invest $10,000 in the Fund over the time periods indicated and then redeem all
of your shares at the end of those periods. The Example also assumes that your
investment has a 5% return each year and that the Fund's operating expenses
remain the same.

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example Jacob Micro Cap Growth Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Investor Class	222	685	1,175	2,524
Institutional Class	187	579	995	2,159

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual fund operating expenses or in the example, affect the Fund's performance.

Principal Investment Strategies

The Fund seeks to achieve its investment objective by investing, under normal
circumstances, at least 80% of its assets in micro capitalization companies.
Micro capitalization companies are defined as those companies with market
capitalizations (share price multiplied by number of shares outstanding)
of (1) less than or equal to $600 million; or (2) within the capitalization
range of the Russell Micro Cap® Growth Index at the time of purchase. As of
August 31, 2012, the market capitalization of the largest company in the Russell
Micro Cap® Growth Index was approximately $837 million, and the weighted average
and median market capitalizations of the Russell Micro Cap® Growth Index were
approximately $322 million and $149 million, respectively.

The Fund maintains a diversified portfolio of investments consisting primarily
of common stocks. The Fund may also invest in other equity securities such as
preferred stocks, securities convertible or exchangeable into common stocks,
rights, warrants, or real estate investment trusts. The Adviser expects to
select investments for the Fund in companies that are broadly diversified over
various industry groups.

The Adviser manages the Fund's portfolio in an aggressive growth style. The
Adviser believes that investments in micro capitalization companies can have
greater earnings and sales growth potential than larger capitalized companies
and can offer substantial opportunities for long-term growth of capital. The
Adviser's overall stock selections are based on its qualitative and quantitative
assessment of a company's fundamental prospects and whether it has an
above-average potential for long-term growth of capital.

The Adviser expects to invest the Fund's net assets primarily in U.S. companies,
but may gain exposure to foreign markets through the global operations of U.S.
companies, by purchasing depositary receipts or securities of foreign companies
traded on U.S. exchanges, or through direct investment in foreign companies. The
Adviser will not invest more than 25% of the Fund's net assets directly in
foreign companies.

The Fund intends to hold some cash, short-term debt obligations, government
securities or other high-quality investments for reserves to cover redemptions
and unanticipated expenses, or to maintain liquidity while seeking appropriate
investments.

Principal Risks

Investing in a mutual fund has inherent risks, which could cause you to lose
money. The principal risks of investing in the Fund, and the circumstances that
could adversely affect the Fund's net asset value and total return, are listed
below.

·  Market Risk: The value of the Fund's shares and the securities held by the    
   Fund can each decline in value. Even when the stock market in general is      
   rising, the stocks selected by the Adviser may decline. Prices of common      
   stocks of even the best managed, most profitable corporations are subject to  
   market risk, which means their stock prices can decline. In addition, swings  
   in investor psychology or significant trading by large institutional investors
   can result in price fluctuations.                                             
  
·  Micro Capitalized Company Risk: Investments in micro capitalization companies
   may involve greater risks, as these companies tend to have limited product    
   lines, markets and financial or managerial resources. Micro cap stocks often  
   also have a more limited trading market, such that the Adviser may not be able
   to sell stocks at an optimal time or price. In addition, less                 
   frequently-traded securities may be subject to more abrupt price movements    
   than securities of larger capitalized companies.   
                           
·  Growth Companies Risk. Growth companies are expected to increase their        
   earnings at a certain rate. When these expectations are not met, the prices of
   these stocks may go down, even if earnings showed an absolute increase. Growth
   company stocks also typically lack the dividend yield that can cushion stock  
   prices in market downturns. Different investment styles tend to shift in and  
   out of favor, depending on market conditions and investor sentiment. The      
   Fund's growth style may cause the Fund to underperform funds that have a      
   broader investment style.                                                     
  
·  Foreign and Emerging Market Risk: The risks of investing in foreign companies,
   including those located in emerging market countries, can increase the potential
   for losses in the Fund and may include currency fluctuations, political and
   economic instability, less government regulation, less publicly available
   information, limited trading markets, differences in financial reporting standards
   and less stringent regulation of securities markets. Foreign securities markets
   generally have less volume than U.S. securities exchanges and securities of some
   foreign companies are less liquid and more volatile than securities of comparable
   U.S. companies. Additional risks include future political and economic developments,
   the possibility that a foreign jurisdiction might impose or increase withholding
   taxes on income payable with respect to foreign securities, the possible seizure,             
   nationalization or expropriation of the foreign issuer or foreign deposits (in
   which the Fund could lose its entire investment in a certain market) and the  
   possible adoption of foreign governmental restrictions such as exchange       
   controls.

Performance Information

Performance information gives some indication of the risks of investing in
the Fund by comparing the Fund's performance with a broad measure of market
performance. Performance information is not presented because the Fund had
not commenced investment operations as of the date of this Prospectus. In
the future, the Fund will disclose performance information in a bar chart
and performance table.

[1] Please note that the percentage of Annual Fund Operating Expenses shown is based on estimated amounts and on the amount of assets expected to transfer into the Fund as a result of the reorganization of the Jacob Micro Cap Growth Fund (formerly PineBridge US Micro Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. If the Fund's average annual net assets during the current fiscal year are lower, the Fund's expense ratio would be higher than that shown above.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Oct. 01, 2012
Jacob Wisdom Fund (Prospectus Summary) | Jacob Wisdom Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	JACOB WISDOM FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is to maximize total investment return consisting of a combination of income and capital appreciation.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 13.60% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	13.60%
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund over the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its investment objective by investing primarily in equity securities of U.S. companies of any size. The Fund may gain exposure to foreign markets through the global operations of U.S. companies, or through direct investment in foreign companies. The Adviser will not invest more than 25% of the Fund's net assets directly in foreign companies. The Fund may, to a lesser extent, invest in investment grade fixed income or debt securities to seek income. The Fund invests in securities of companies that the Adviser believes have the greatest potential for capital appreciation and income. The Adviser's overall stock selections are based on an assessment of a company's fundamental prospects. Specifically, the Adviser uses fundamental analysis to assess the quality, growth potential, financial strength and overall value of a company. While trying to maximize the capital appreciation potential of the Fund's portfolio of investments, the Adviser also seeks to obtain securities for the Fund that are selling at reasonable prices. The Fund maintains a diversified portfolio of investments consisting primarily of common stocks, and may also invest in other equity securities such as preferred stocks, securities convertible or exchangeable into common stock, rights, warrants or real estate investment trusts (REITs). Equity securities generally represent an ownership interest in a company and their value is based on the success of the company's business, any income paid to shareholders, the value of the company's assets, general market conditions and investor demand. The Fund may also purchase depositary receipts, which are certificates normally issued by U.S. banks that evidence the ownership of shares of a foreign company. The Fund generally seeks to purchase securities as long-term investments, but when circumstances warrant, securities may be sold without regard to the length of time they have been held to reduce risk or volatility or to respond to changing fundamental information. The Fund intends to hold some cash, short-term debt obligations, government securities or other high-quality investments for reserves to cover redemptions and unanticipated expenses, to seek income, or to maintain liquidity while seeking appropriate investments.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Investing in a mutual fund has inherent risks, which could cause you to lose money. The principal risks of investing in the Fund, and the circumstances that could adversely affect the Fund's net asset value and total return, are listed below. ·  Market Risk: Even when the stock market in general is rising, the stocks          selected by the Adviser may decline. Prices of common stocks of even the best    managed, most profitable corporations are subject to market risk, which means    their stock prices can decline. In addition, swings in investor psychology or    significant trading by large institutional investors can result in price          fluctuations. The Adviser may not be able to sell stocks at an optimal time    or price.                                                                            ·  Smaller Capitalized Company Risk: Investments in smaller capitalized companies    may involve greater risks, as these companies may not have the management         experience, financial resources, product diversification and competitive          strengths of larger companies.                                                 ·  Convertible Securities Risk: The market value of convertible securities tends    to decline as interest rates increase and, conversely, to increase as interest    rates decline. In addition, convertible securities generally offer lower          interest or dividend yields than non-convertible securities of similar            quality.                                                                          ·  Fixed Income Risk: Yields and principal values of fixed income securities         (bonds) will fluctuate. Generally, values of fixed income securities change       inversely with interest rates. As interest rates go up, the value of debt         securities tends to go down. As a result, to the extent the Fund holds fixed      income investments, the value of the Fund may go down. The issuers of             instruments in which the Fund invests may be unable to meet interest and/or       principal payments. An issuer's securities may decrease in value if its           financial strength weakens, which may reduce its credit rating and possibly       its ability to meet its contractual obligations.                                  ·  Foreign Risk: The risks of investing in foreign companies can increase the        potential for losses in the Fund and may include currency fluctuations,           political and economic instability, less government regulation, less publicly    available information, limited trading markets, differences in financial          reporting standards and less stringent regulation of securities markets.    Foreign securities markets generally have less volume than U.S. securities    exchanges and securities of some foreign companies are less liquid and more    volatile than securities of comparable U.S. companies. Additional risks    include future political and economic developments, the possibility that    a foreign jurisdiction might impose or increase withholding taxes on income       payable with respect to foreign securities, the possible seizure,nationalization    or expropriation of the foreign issuer or foreign deposits (in which the Fund    could lose its entire investment in a certain market) and the possible adoption    of foreign governmental restrictions such as exchange controls.                                                                      ·  Real Estate Investment Trust Risk: Investments in real estate related             instruments may be affected by economic, legal, cultural, environmental or        technological factors that affect property values, rents or occupancies of        real estate related to the Fund's holdings. The performance of REITs depends      on how well the REIT manages the properties it owns.
Risk Lose Money [Text]	rr_RiskLoseMoney	Investing in a mutual fund has inherent risks, which could cause you to lose money.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The performance information that follows gives some indication of the risks of investing in the Fund. The bar chart shows the Fund's performance from year to year, and the table compares the Fund's average annual returns with those of a broad measure of market performance. Please note that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The performance information that follows gives some indication of the risks of investing in the Fund.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Please note that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns as of December 31, 2011 (Investor Class)
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	As of September 30, 2012, the Fund's year to date return was 14.40%. Best Quarter       Q1     2012      9.56% Worst Quarter      Q3     2011     -9.08%
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	reflects no deduction for fees, expenses or taxes
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.
Performance Table Explanation after Tax Higher	rr_PerformanceTableExplanationAfterTaxHigher	The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	The performance information shown is for the period from December 1, 2009 to December 31, 2011. The performance information shown for the period from December 1, 2009, to February 17, 2010, is that of the Fund's predecessor, the Wisdom Fund. The Adviser took over management of the Wisdom Fund on December 1, 2009, and the Wisdom Fund was reorganized into the Jacob Wisdom Fund on February 18, 2010. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns as of December 31, 2011
Jacob Wisdom Fund (Prospectus Summary) | Jacob Wisdom Fund | S&P® 500 Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	S&P® 500 Index (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	2.11%
Since Inception	rr_AverageAnnualReturnSinceInception	8.42%
Jacob Wisdom Fund (Prospectus Summary) | Jacob Wisdom Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	(2.00%)
Advisory Fees	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.35%
Other Expenses	rr_OtherExpensesOverAssets	1.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.82%
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.50%)	[1]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	2.32%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-01-02
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	235
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	827
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,445
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	3,111
Annual Return 2010	rr_AnnualReturn2010	11.52%
Annual Return 2011	rr_AnnualReturn2011	3.59%
Year to Date Return, Label	rr_YearToDateReturnLabel	year to date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	14.40%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jan. 31, 2012
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	9.56%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(9.08%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	3.59%
Since Inception	rr_AverageAnnualReturnSinceInception	7.52%
Jacob Wisdom Fund (Prospectus Summary) | Jacob Wisdom Fund | Investor Class | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	3.22%
Since Inception	rr_AverageAnnualReturnSinceInception	7.31%
Jacob Wisdom Fund (Prospectus Summary) | Jacob Wisdom Fund | Investor Class | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	2.33%
Since Inception	rr_AverageAnnualReturnSinceInception	6.32%

[1] Jacob Asset Management of New York LLC, the Fund's investment adviser (the "Adviser"), has contractually agreed , through at least January 2, 2014, to waive up to 100% of its advisory fees, to the extent that the Total Annual Fund Operating Expenses (excluding any taxes, interest, brokerage fees, and extraordinary expenses) would exceed 1.95% of average daily net assets. This fee waiver agreement does not extend to indirect expenses of any acquired funds. Pursuant to this fee waiver agreement, the Adviser is entitled to recoup any fees that it waived for a period of three years following such fee waivers to the extent that such recoupment will not cause the Fund's expenses to exceed 1.95%. Please note that the maximum waiver is 0.50%, which means that the Fund's overall expenses could exceed 1.95%, as is the case above. This waiver agreement may only be terminated by the Board.

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Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund

JACOB SMALL CAP GROWTH FUND

Investment Objective

The Fund's investment objective is long-term growth of capital.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the Fund.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees Jacob Small Cap Growth Fund	Investor Class	Institutional Class
Maximum Sales Charge (Load) Imposed on Purchases	none	none
Maximum Deferred Sales Charge (Load)	none	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	none	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	2.00%	none

Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)

Annual Fund Operating Expenses Jacob Small Cap Growth Fund		Investor Class	Institutional Class
Advisory Fees		0.90%	0.90%
Distribution and/or Service (12b-1) Fees		0.35%	none
Other Expenses		1.18%	1.18%
Total Annual Fund Operating Expenses		2.43%	2.08%
Fee Waiver	[1]	(0.18%)	(0.13%)
Total Annual Fund Operating Expenses After Fee Waiver	[2]	2.25%	1.95%

Example:

This example is intended to help you compare the cost of investing in the Fund
with the cost of investing in other mutual funds. The Example assumes that you
invest $10,000 in the Fund over the time periods indicated and then redeem all
of your shares at the end of those periods. The Example also assumes that your
investment has a 5% return each year and that the Fund's operating expenses
remain the same.

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example Jacob Small Cap Growth Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Investor Class	228	740	1,279	2,753
Institutional Class	198	639	1,107	2,400

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual fund operating expenses or in the example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 102.80%
of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objective by investing, under normal
circumstances, at least 80% of its assets in small capitalization companies.
Small capitalization companies are defined as those companies with market
capitalizations (share price multiplied by number of shares outstanding)
within the capitalization range of the Russell 2000® Growth Index at the time
of purchase.  As of August 31, 2012, the market capitalization of the largest
company in the Russell 2000® Growth Index was approximately $4.621 billion,
and the weighted average and median market capitalizations of the Russell 2000®
Growth Index were approximately $1.431 billion and $584 million, respectively.

The Fund maintains a diversified portfolio of investments consisting primarily
of common stocks. The Fund may also invest in other equity securities such as
preferred stocks, securities convertible or exchangeable into common stocks,
rights, warrants, or real estate investment trusts. The Adviser expects to
select investments for the Fund in companies that are broadly diversified over
various industry groups.

The Adviser manages the Fund's portfolio in an aggressive growth style. The
Adviser believes that investments in small capitalization companies can have
greater earnings and sales growth potential than larger capitalized companies
and can offer substantial opportunities for long-term growth of capital. The
Adviser's overall stock selections are based on its qualitative and quantitative
assessment of a company's fundamental prospects and whether it has an
above-average potential for long-term growth of capital.

The Adviser expects to invest the Fund's net assets primarily in U.S. companies,
but may gain exposure to foreign markets through the global operations of U.S.
companies, by purchasing depositary receipts or securities of foreign companies
traded on U.S. exchanges, or through direct investment in foreign companies. The
Adviser will not invest more than 25% of the Fund's net assets directly in
foreign companies.

The Fund intends to hold some cash, short-term debt obligations, government
securities or other high-quality investments for reserves to cover redemptions
and unanticipated expenses, or to maintain liquidity while seeking appropriate
investments.

Principal Risks

Investing in a mutual fund has inherent risks, which could cause you to lose
money. The principal risks of investing in the Fund, and the circumstances that
could adversely affect the Fund's net asset value and total return, are listed
below.

·  Market Risk: The value of the Fund's shares and the securities held by the    
   Fund can each decline in value. Even when the stock market in general is      
   rising, the stocks selected by the Adviser may decline. Prices of common      
   stocks of even the best managed, most profitable corporations are subject to  
   market risk, which means their stock prices can decline. In addition, swings  
   in investor psychology or significant trading by large institutional investors
   can result in price fluctuations.                                             
  
·  Smaller Capitalized Company Risk: Investments in small capitalization         
   companies may involve greater risks, as these companies tend to have limited  
   product lines, markets and financial or managerial resources. Small cap stocks
   often also have a more limited trading market, such that the Adviser may not  
   be able to sell stocks at an optimal time or price. In addition, less         
   frequently-traded securities may be subject to more abrupt price movements    
   than securities of larger capitalized companies.                              
  
·  Growth Companies Risk. Growth companies are expected to increase their        
   earnings at a certain rate. When these expectations are not met, the prices of
   these stocks may go down, even if earnings showed an absolute increase. Growth
   company stocks also typically lack the dividend yield that can cushion stock  
   prices in market downturns. Different investment styles tend to shift in and  
   out of favor, depending on market conditions and investor sentiment. The      
   Fund's growth style may cause the Fund to underperform funds that have a      
   broader investment style.                                                     

·  Foreign and Emerging Market Risk: The risks of investing in foreign companies,
   including those located in emerging market countries, can increase the potential
   for losses in the Fund and may include currency fluctuations, political and
   economic instability, less government regulation, less publicly available
   information, limited trading markets, differences in financial reporting standards
   and less stringent regulation of securities markets. Foreign securities markets
   generally have less volume than U.S. securities exchanges and securities of some
   foreign companies are less liquid and more volatile than securities of comparable
   U.S. companies. Additional risks include future political and economic developments,
   the possibility that a foreign jurisdiction might impose or increase withholding
   taxes on income payable with respect to foreign securities, the possible seizure,             
   nationalization or expropriation of the foreign issuer or foreign deposits (in
   which the Fund could lose its entire investment in a certain market) and the  
   possible adoption of foreign governmental restrictions such as exchange       
   controls.

Performance Information

The performance information that follows gives some indication of the risks of
investing in the Fund. The bar chart shows the Fund's performance for the last
calendar year, and the table compares the Fund's average annual returns with
those of a broad measure of market performance. Please note that the Fund's past
performance (before and after taxes) is not necessarily an indication of how the
Fund will perform in the future. Performance information is not presented for
Institutional Class shares of the Fund because the Fund had not issued
Institutional Class shares as of the date of this Prospectus.

Annual Total Returns as of December 31, 2011 (Investor Class)

As of September 30, 2012, the Fund's year to date return was 14.52%.

Best Quarter       Q4     2010      22.86%
Worst Quarter      Q3     2011     -27.18%

Average Annual Total Returns as of December 31, 2011

Average Annual Total Returns Jacob Small Cap Growth Fund	Label	1 Year	Since Inception	Inception Date
Investor Class	Return Before Taxes	(13.93%)	10.05%	Feb. 01, 2010
Investor Class After Taxes on Distributions	Return After Taxes on Distributions	(15.34%)	9.10%	Feb. 01, 2010
Investor Class After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	(9.05%)	8.05%	Feb. 01, 2010
Institutional Class	Return Before Taxes			Feb. 01, 2010
Russell 2000® Growth Index	Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)	(2.91%)	14.51%	Feb. 01, 2010

After-tax returns are calculated using the historical highest individual federal
marginal income tax rates and do not reflect the impact of state and local
taxes. Actual after-tax returns depend on an investor's tax situation and may
differ from those shown. After-tax returns shown are not relevant to investors
who hold their Fund shares through tax-deferred arrangements such as 401(k)
plans or individual retirement accounts. The return after taxes on distribution
and sale of fund shares may be higher than the return before taxes because the
method of calculation assumes generally that you can use the short-term capital
loss realized upon the sale of fund shares to offset income of the same tax
character from other sources thereby reducing the amount of tax you otherwise
might owe.

[1] Jacob Asset Management of New York LLC, the Fund's investment adviser (the "Adviser"), has contractually agreed, through at least January 2, 2014, to waive up to 100% of its advisory fees to the extent that the Total Annual Fund Operating Expenses (excluding any taxes, interest, brokerage fees, and extraordinary expenses) exceed 2.25% or 1.95% for Investor Class shares and Institutional Class shares, respectively, of each class' average daily net assets. This fee waiver agreement does not extend to indirect expenses of any acquired funds. Pursuant to this fee waiver agreement, the Adviser is entitled to recoup any fees that it waived for a period of three years following such fee waivers to the extent that such recoupment will not cause the Fund to exceed any applicable expense limitation that was in place for the Fund when the fees were waived. Please note that the maximum waiver is 0.90%, which means that the Fund's overall expenses could exceed 2.25% for Investor Class shares or 1.95% for Institutional Class shares. This waiver agreement may only be terminated by the Board. Please also note that this fee waiver agreement is contingent upon the closing of the reorganization of the Jacob Small Cap Growth Fund II (formerly PineBridge US Small Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. Otherwise the fee waiver agreement currently in place for Investor Class shares of the Fund (which operates as described above with fees waived if expenses exceed 2.45%) will apply through at least January 2, 2014.

[2] Please note that the percentage of Annual Fund Operating Expenses shown is based on estimated amounts and on the amount of assets expected to transfer into the Fund as a result of the reorganization of the Jacob Small Cap Growth Fund II (formerly PineBridge US Small Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. If the Fund's average annual net assets during the current fiscal year are lower, the Fund's expense ratio would be higher than that shown above.

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Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Oct. 01, 2012
Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro Cap Growth Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	JACOB MICRO CAP GROWTH FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is long-term growth of capital.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses paid each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund over the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its assets in micro capitalization companies. Micro capitalization companies are defined as those companies with market capitalizations (share price multiplied by number of shares outstanding) of (1) less than or equal to $600 million; or (2) within the capitalization range of the Russell Micro Cap® Growth Index at the time of purchase. As of August 31, 2012, the market capitalization of the largest company in the Russell Micro Cap® Growth Index was approximately $837 million, and the weighted average and median market capitalizations of the Russell Micro Cap® Growth Index were approximately $322 million and $149 million, respectively. The Fund maintains a diversified portfolio of investments consisting primarily of common stocks. The Fund may also invest in other equity securities such as preferred stocks, securities convertible or exchangeable into common stocks, rights, warrants, or real estate investment trusts. The Adviser expects to select investments for the Fund in companies that are broadly diversified over various industry groups. The Adviser manages the Fund's portfolio in an aggressive growth style. The Adviser believes that investments in micro capitalization companies can have greater earnings and sales growth potential than larger capitalized companies and can offer substantial opportunities for long-term growth of capital. The Adviser's overall stock selections are based on its qualitative and quantitative assessment of a company's fundamental prospects and whether it has an above-average potential for long-term growth of capital. The Adviser expects to invest the Fund's net assets primarily in U.S. companies, but may gain exposure to foreign markets through the global operations of U.S. companies, by purchasing depositary receipts or securities of foreign companies traded on U.S. exchanges, or through direct investment in foreign companies. The Adviser will not invest more than 25% of the Fund's net assets directly in foreign companies. The Fund intends to hold some cash, short-term debt obligations, government securities or other high-quality investments for reserves to cover redemptions and unanticipated expenses, or to maintain liquidity while seeking appropriate investments.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Investing in a mutual fund has inherent risks, which could cause you to lose money. The principal risks of investing in the Fund, and the circumstances that could adversely affect the Fund's net asset value and total return, are listed below. ·  Market Risk: The value of the Fund's shares and the securities held by the        Fund can each decline in value. Even when the stock market in general is          rising, the stocks selected by the Adviser may decline. Prices of common          stocks of even the best managed, most profitable corporations are subject to      market risk, which means their stock prices can decline. In addition, swings      in investor psychology or significant trading by large institutional investors    can result in price fluctuations.                                                 ·  Micro Capitalized Company Risk: Investments in micro capitalization companies    may involve greater risks, as these companies tend to have limited product        lines, markets and financial or managerial resources. Micro cap stocks often      also have a more limited trading market, such that the Adviser may not be able    to sell stocks at an optimal time or price. In addition, less                     frequently-traded securities may be subject to more abrupt price movements        than securities of larger capitalized companies.                                ·  Growth Companies Risk. Growth companies are expected to increase their            earnings at a certain rate. When these expectations are not met, the prices of    these stocks may go down, even if earnings showed an absolute increase. Growth    company stocks also typically lack the dividend yield that can cushion stock      prices in market downturns. Different investment styles tend to shift in and      out of favor, depending on market conditions and investor sentiment. The          Fund's growth style may cause the Fund to underperform funds that have a          broader investment style.                                                         ·  Foreign and Emerging Market Risk: The risks of investing in foreign companies,    including those located in emerging market countries, can increase the potential    for losses in the Fund and may include currency fluctuations, political and    economic instability, less government regulation, less publicly available    information, limited trading markets, differences in financial reporting standards    and less stringent regulation of securities markets. Foreign securities markets    generally have less volume than U.S. securities exchanges and securities of some    foreign companies are less liquid and more volatile than securities of comparable    U.S. companies. Additional risks include future political and economic developments,    the possibility that a foreign jurisdiction might impose or increase withholding    taxes on income payable with respect to foreign securities, the possible seizure,                 nationalization or expropriation of the foreign issuer or foreign deposits (in    which the Fund could lose its entire investment in a certain market) and the      possible adoption of foreign governmental restrictions such as exchange           controls.
Risk Lose Money [Text]	rr_RiskLoseMoney	Investing in a mutual fund has inherent risks, which could cause you to lose money.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	Performance information gives some indication of the risks of investing in the Fund by comparing the Fund's performance with a broad measure of market performance. Performance information is not presented because the Fund had not commenced investment operations as of the date of this Prospectus. In the future, the Fund will disclose performance information in a bar chart and performance table.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Performance information gives some indication of the risks of investing in the Fund by comparing the Fund's performance with a broad measure of market performance.
Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro Cap Growth Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	(2.00%)
Advisory Fees	rr_ManagementFeesOverAssets	1.20%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.35%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.19%	[1]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	222
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	685
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,175
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,524
Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro Cap Growth Fund | Institutional Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	none
Advisory Fees	rr_ManagementFeesOverAssets	1.20%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.84%	[1]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	187
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	579
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	995
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,159

[1] Please note that the percentage of Annual Fund Operating Expenses shown is based on estimated amounts and on the amount of assets expected to transfer into the Fund as a result of the reorganization of the Jacob Micro Cap Growth Fund (formerly PineBridge US Micro Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. If the Fund's average annual net assets during the current fiscal year are lower, the Fund's expense ratio would be higher than that shown above.