0000031266
2013-01-29
2013-01-29
0000031266
EVSIT:S000039655Member
2013-01-29
2013-01-29
0000031266
EVSIT:S000039655Member
EVSIT:C000122821Member
2013-01-29
2013-01-29
0000031266
EVSIT:S000039655Member
EVSIT:C000122823Member
2013-01-29
2013-01-29
iso4217:USD
xbrli:pure
485BPOS
2012-10-31
Eaton Vance Special Investment Trust
0000031266
false
2013-01-29
2013-01-29
2013-01-29
<p style="font: 12pt Times New Roman, Times, Serif; margin: 3.75pt 0">Investment Objective</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">The Fund’s investment objective is total return.</p>
<p style="font: 12pt Times New Roman, Times, Serif; margin: 3.75pt 0">Fees and Expenses of the Fund</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">This table describes the fees and expenses that you may pay
if you buy and hold shares of the Fund.  You may qualify for a reduced sales charge if you invest, or agree to invest over
a 13-month period, at least $50,000 in Eaton Vance Funds.  More information about these and other discounts is available from
your financial intermediary and in Sales Charges beginning on page 16 of this Prospectus and page 19 of the Fund’s Statement
of Additional Information.</p>
<div style="display: none">~ http://xbrl.sec.gov/rr/role/ShareholderFeesData column period compact * column dei_LegalEntityAxis compact EVSIT_S000039655Member column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<p style="font: 12pt Times New Roman, Times, Serif; margin: 3.75pt 0">Portfolio Turnover</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">The Fund and the Portfolios in which it invests (see below)
pay transaction costs, such as commissions, when they buy and sell securities (or “turns over” the 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.</p>
<p style="font: 12pt Times New Roman, Times, Serif; margin: 3.75pt 0">Principal Investment Strategies</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Under normal market conditions, the Fund invests at least
80% of its net assets in bonds and other income instruments (the “80% Policy”).  Bonds and other income instruments
include, among other things, corporate bonds and other fixed income securities, senior and junior loans, U.S. government securities,
commercial paper, mortgage-related securities (including commercial mortgage-backed securities , mortgage dollar rolls, stripped
mortgage-related securities and collateralized mortgage obligations) and other asset-backed securities (including collateralized
debt obligations), zero-coupon securities, when-issued securities, repurchase agreements, foreign debt securities (including those
located in emerging market countries), sovereign debt (including debt issued by emerging market countries),   obligations
of supranational entities, structured notes, private placements, preferred securities and convertible securities. The Fund may
invest up to 35% of its net assets in bonds and other income instruments rated below investment grade (i.e. rated lower than BBB
by Standard & Poor’s Ratings Group (“S&P ”) or lower than Baa by Moody’s Investors Service, Inc.
(“Moody’s”) or by Fitch Ratings (“Fitch ”)) and in unrated instruments determined by the investment
adviser to be of below investment grade quality (“junk bonds”) (the “35% Policy”). The Fund may invest
in income instruments of any maturity. The Fund may invest up to 20% of its net assets in common stocks and other equity securities,
including real estate investment trusts. The Fund may engage in derivatives transactions, including futures contracts and options
thereon, forwards and credit default swaps. The Fund expects to principally use derivatives to manage interest rate and credit
risk or otherwise for investment purposes.  Positions in derivatives that have economic characteristics similar to bonds or
other income instruments will be treated as bonds and other income instruments for purposes of the Fund’s 80% Policy and
35% Policy.  The Fund is “non-diversified”, which means it may invest a greater percentage of its assets in the
securities of a single issuer than a “diversified” fund.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">In managing the Fund, the investment adviser will employ a
bottom-up, research driven approach that emphasizes the financial strength of issuers, current interest rates, current valuations,
the interest rate sensitivity of investments and the investment adviser’s interest rate expectations, the stability and volatility
of a country’s bond markets, and expectations regarding general trends in global economies and currencies. The investment
adviser also will consider how purchasing or selling a bond would impact the overall portfolio’s risk profile (for example,
its sensitivity to currency risk, interest rate risk and sector-specific risk) and potential return (income and capital gains).
For its equity investments, the Fund primarily seeks dividend-paying stocks of companies that the investment adviser believes to
have strong fundamentals and attractive valuations.  The investment adviser generally selects individual securities with an
investment horizon of two to five years.  </p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">The Fund is structured as a “fund-of-funds” and
seeks to achieve its investment objective primarily by investing in one or more of the following registered investment companies
managed by Eaton Vance Management or its affiliates: Bond Portfolio, CMBS Portfolio and Floating Rate Portfolio (each, a “Portfolio”).
 The Fund may also invest directly in securities and other instruments.   Total return is defined as income plus capital
appreciation.  Each Portfolio is described in “Further Information about the Portfolios” in the Fund’s Prospectus. 
In making allocation decisions, the investment adviser takes market and other factors into consideration.</p>
<p style="font: 12pt Times New Roman, Times, Serif; margin: 3.75pt 0">Principal Risks</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Market Risk.  Economic and other events (whether real
or perceived) can reduce the demand for investments held by the Fund, which may reduce their market prices and cause the value
of Fund shares to fall. The frequency and magnitude of such changes cannot be predicted.  Certain securities and other investments
held by the Fund can experience downturns in trading activity and, at such times, the supply of such instruments in the market
may exceed the demand.  At other times, the demand for such instruments may exceed the supply in the market.  An imbalance
in supply and demand in the market may result in valuation uncertainties and greater volatility, less liquidity, wider trading
spreads and a lack of price transparency in the market.  No active trading market may exist for certain investments, which
may impair the ability of the Fund to sell or to realize the full value of such investments in the event of the need to liquidate
such assets. Adverse market conditions may impair the liquidity of some actively traded investments.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Risk of Lower Rated Investments.<i> </i> Investments
rated below investment grade and comparable unrated investments (“junk bonds”) have speculative characteristics because
of the credit risk associated with their issuers.  Changes in economic conditions or other circumstances typically have a
greater effect on the ability of issuers of lower rated investments to make principal and interest payments than they do on issuers
of higher rated investments.  An economic downturn generally leads to a higher non-payment rate, and a lower rated investment
may lose significant value before a default occurs.  Lower rated investments typically are subject to greater price volatility
and illiquidity than higher rated investments.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Foreign and Emerging Market Investment Risk.<font style="font-family: Arial, Helvetica, Sans-Serif"> </font>Because
the Fund can invest a portion of its assets in foreign instruments, the value of Fund shares can be adversely affected by changes
in currency exchange rates and political, economic and market developments abroad.  In emerging or less developed countries,
these risks can be more significant.  Investment markets in emerging market countries are typically substantially smaller,
less liquid and more volatile than the major markets in developed countries.  As a result, Fund share values may be more volatile
than if the Fund invested only in developed markets.  Emerging market countries may have relatively unstable governments and
economies.  Emerging market investments often are subject to speculative trading, which typically contributes to volatility.
 Trading in foreign and emerging markets typically involves higher expense than trading in the United States. The Fund may
have difficulties enforcing its legal or contractual rights in a foreign country. The value of investments denominated in foreign
currencies can be adversely affected by changes in foreign currency exchange rates. Depository receipts are subject to many of
the risks associated with investing directly in foreign securities including political and economic risks.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Interest Rate Risk.  As interest rates rise, the value
of Fund shares is likely to decline.  Conversely, when interest rates decline, the value of Fund shares is likely to rise.
 Securities with longer maturities are more sensitive to changes in interest rates than those with shorter maturities, making
them more volatile.  A rising interest rate environment may extend the average life of mortgages or other asset-backed receivables
underlying mortgage-backed or asset-backed securities. This extension increases the risk of depreciation due to future increases
in market interest rates.  In a declining interest rate environment, prepayment of callable income investments may increase.
 In such circumstances, the Fund may have to reinvest the prepayment proceeds at lower yields.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Credit Risk.<i>  </i>Investments in debt obligations
are subject to the risk of non-payment of scheduled principal and interest.  Changes in economic conditions or other circumstances
may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults.
Such non-payments and defaults may reduce the value of Fund shares and income distributions. The value of a debt obligation also
may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit
ratings of income instruments may be lowered if the financial condition of the party obligated to make payments with respect to
such instruments changes.  Credit ratings assigned by rating agencies are based on a number of factors and do not necessarily
reflect the issuer’s current financial condition or the volatility or liquidity of the security.  In the event of bankruptcy
of the issuer of income instruments, the Fund could experience delays or limitations with respect to its ability to realize the
benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar
situation, the Fund may be required to retain legal or similar counsel.  This may increase the Fund’s operating expenses
and adversely affect net asset value.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Derivatives Risk. <i> </i>The use of derivatives can
lead to losses because of adverse movements in the price or value of the asset, index, rate or instrument underlying a derivative,
due to failure of a counterparty or due to tax or regulatory constraints.  Derivatives may create economic leverage in the
Fund, which magnifies the Fund’s exposure to the underlying investment. Derivatives risk may be more significant when derivatives
are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position
held by the Fund.  When derivatives are used to gain or limit exposure to a particular market or market segment, their performance
may not correlate as expected to the performance of such market thereby causing the Fund to fail to achieve its original purpose
for using such derivatives. A decision as to whether, when and how to use derivatives involves the exercise of specialized skill
and judgment, and a transaction may be unsuccessful in whole or in part because of market behavior or unexpected events.  Derivative
instruments may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the
value of the underlying instrument.  If a derivative’s counterparty is unable to honor its commitments, the value of
Fund shares may decline and the Fund could experience delays in the return of collateral or other assets held by the counterparty.
 The loss on derivative transactions may substantially exceed the initial investment.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Risk of Senior Loans.<i> </i> Risks of investments in
Senior Loans are similar to the risks of lower rated securities, although interest rate risk may be reduced because Senior Loan
rates generally are adjusted for changes in short-term interest rates.  Junior Loans are subject to the same general risks.
 Due to their lower place in the borrower’s capital structure and possible unsecured status, Junior Loans may involve
a higher degree of overall risk than Senior Loans of the same borrower.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Commercial Mortgage-Backed Securities Risk.   Commercial
mortgage-backed securities (“CMBS”) are subject to credit, interest rate, prepayment and extension risk. CMBS may not
be backed by the full faith and credit of the U.S. Government and are subject to risk of default on the underlying mortgage. CMBS
issued by non-government entities may offer higher yields than those issued by government entities, but also may be subject to
greater volatility than government issues. CMBS react differently to changes in interest rates than other bonds and the prices
of CMBS may reflect adverse economic and market conditions. Small movements in interest rates (both increases and decreases) may
quickly and significantly reduce the value of CMBS.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Risk of Leveraged Transactions.  Certain Fund transactions
may give rise to a form of leverage.  Such transactions may include, among others, repurchase agreements, dollar rolls, borrowing,
loans of portfolio securities and the use of when-issued, delayed delivery or forward commitment transactions, short sales and
certain derivative transactions.  The Fund is required to segregate liquid assets or otherwise cover the Fund’s obligation
created by a transaction that may give rise to leverage.  The use of leverage may cause the Fund to liquidate portfolio positions
when it may not be advantageous to do so to satisfy its obligations or to meet segregation requirements.  Leverage may cause
the Fund to be more volatile than if it had not been leveraged, as certain types of leverage may exaggerate the effect of any increase
or decrease in the value of the Fund’s portfolio securities.  The loss on leveraged transactions may substantially exceed
the initial investment.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Equity Investing Risk. The Fund’s shares may be sensitive
to stock market volatility.  The value of equity investments and related instruments may decline in response to conditions
affecting the general economy; overall market changes; local, regional or global political, social or economic instability; and
currency, interest rate and commodity price fluctuations, as well as issuer or sector specific events. Although values can rebound,
there is no assurance they will return to previous levels.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Risk of U.S. Government-Sponsored Agencies.  Although
certain U.S. Government-sponsored agencies (such as the Federal Home Loan Mortgage Corporation and the Federal National Mortgage
Association) may be chartered or sponsored by acts of Congress, their securities are neither issued nor guaranteed by the U.S.
Treasury.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Risks of Repurchase Agreements.  In the event of the
insolvency of the counterparty to a repurchase agreement, recovery of the repurchase price owed to the Fund may be delayed. Such
an insolvency also may result in a loss to the extent that the value of the purchased securities decreases during the delay or
that value has otherwise not been maintained at an amount at least equal to the repurchase price.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Real Estate Investment Trust Risk.  Real estate investment
trusts (“REITs”) are subject to special risks associated with real estate.  Securities of companies in the real
estate industry are sensitive to factors such as changes in real estate values, property taxes, interest rates, cash flow of underlying
real estate assets, occupancy rates, government regulations affecting zoning, land use, and rents, and the management skill and
creditworthiness of the issuer.  Companies in the real estate industry may also be subject to liabilities under environmental
and hazardous waste laws, among others.  Changes in underlying real estate values may have an exaggerated effect to the extent
that REITs concentrate investments in particular geographic regions or property types.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Issuer Diversification Risk. The Fund is “non-diversified”
which means it may invest a greater percentage of its assets in the securities of a single issuer than funds that are “diversified.”
 Non-diversified funds face the risk of focusing investments in a small number of issuers, making them more susceptible to
risks affecting such issuers than a more diversified fund might be.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Risks Associated with Active Management.  The Fund is
an actively managed portfolio and its success depends upon the investment skills and analytical abilities of the investment adviser
to develop and effectively implement strategies to achieve the Fund’s investment objective.  Subjective decisions made
by the investment adviser may cause the Fund to incur losses or to miss profit opportunities on which it may otherwise have capitalized.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">General Fund Investing Risks.  The Fund is not a complete
investment program and you may lose money by investing in the Fund.  All investments carry a certain amount of risk and there
is no guarantee that the Fund will be able to achieve its investment objective.  Annual Fund Operating Expenses expressed
as a percentage of the Fund’s average daily net assets may change as Fund assets increase and decrease, and Annual Fund Operating
Expenses may differ in the future.  Purchase and redemption activities by Fund shareholders may impact the management of the
Fund and its ability to achieve its investment objective.  In addition, the redemption by one or more large shareholders or
groups of shareholders of their holdings in the Fund could have an adverse impact on the remaining shareholders in the Fund.  Investors
in the Fund should have a long-term investment perspective and be able to tolerate potentially sharp declines in value. An investment
in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other
government agency, entity or person.  Mutual funds, investment advisers, other market participants and many securities markets
are subject to rules and regulations and the jurisdiction of one or more regulators.  Changes to applicable rules and regulations
could have an adverse affect on securities markets and market participants, as well as on the Fund’s ability to execute its
investment strategy.</p>
<p style="font: 12pt Times New Roman, Times, Serif; margin: 3.75pt 0">Performance</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Performance history will be available for the Fund after the
Fund has been in operation for one full calendar year.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Example.  </p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">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 for
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 operating expenses remain the same.  Although your actual costs may
be higher or lower, based on these assumptions your costs would be:</p>
<div style="display: none">~ http://xbrl.sec.gov/rr/role/OperatingExpensesData column period compact * column dei_LegalEntityAxis compact EVSIT_S000039655Member column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<p style="font: 12pt/12pt NewsGoth Dm BT,Times New Roman; margin-top: 4px; margin-bottom: 4px">Shareholder Fees (fees paid directly from your investment)</p>
<p style="font: 12pt/12pt NewsGoth Dm BT,Times New Roman; margin-top: 4px; margin-bottom: 4px">Annual Fund Operating Expenses (expenses you pay each year as a percentage of the value of your investment)</p>
<div style="display: none">~ http://xbrl.sec.gov/rr/role/ExpenseExample column period compact * column dei_LegalEntityAxis compact EVSIT_S000039655Member column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
0.0475
0
0
0
0.0000
0.0000
0.0025
0
0.0022
0.0022
0.0113
0.0088
0.0095
0.0070
567
72
794
256
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">You may qualify for a reduced sales charge if you invest, or agree to invest over
a 13-month period, at least $50,000 in Eaton Vance Funds.  More information about these and other discounts is available from
your financial intermediary and in Sales Charges beginning on page 16 of this Prospectus and page 19 of the Fund’s Statement
of Additional Information.</p>
50000
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Under normal market conditions, the Fund invests at least
80% of its net assets in bonds and other income instruments (the “80% Policy”).  Bonds and other income instruments
include, among other things, corporate bonds and other fixed income securities, senior and junior loans, U.S. government securities,
commercial paper, mortgage-related securities (including commercial mortgage-backed securities , mortgage dollar rolls, stripped
mortgage-related securities and collateralized mortgage obligations) and other asset-backed securities (including collateralized
debt obligations), zero-coupon securities, when-issued securities, repurchase agreements, foreign debt securities (including those
located in emerging market countries), sovereign debt (including debt issued by emerging market countries),   obligations
of supranational entities, structured notes, private placements, preferred securities and convertible securities. The Fund may
invest up to 35% of its net assets in bonds and other income instruments rated below investment grade (i.e. rated lower than BBB
by Standard & Poor’s Ratings Group (“S&P ”) or lower than Baa by Moody’s Investors Service, Inc.
(“Moody’s”) or by Fitch Ratings (“Fitch ”)) and in unrated instruments determined by the investment
adviser to be of below investment grade quality (“junk bonds”) (the “35% Policy”). The Fund may invest
in income instruments of any maturity. The Fund may invest up to 20% of its net assets in common stocks and other equity securities,
including real estate investment trusts. The Fund may engage in derivatives transactions, including futures contracts and options
thereon, forwards and credit default swaps. The Fund expects to principally use derivatives to manage interest rate and credit
risk or otherwise for investment purposes.  Positions in derivatives that have economic characteristics similar to bonds or
other income instruments will be treated as bonds and other income instruments for purposes of the Fund’s 80% Policy and
35% Policy.  The Fund is “non-diversified”, which means it may invest a greater percentage of its assets in the
securities of a single issuer than a “diversified” fund.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">Issuer Diversification Risk. The Fund is “non-diversified”
which means it may invest a greater percentage of its assets in the securities of a single issuer than funds that are “diversified.”
 Non-diversified funds face the risk of focusing investments in a small number of issuers, making them more susceptible to
risks affecting such issuers than a more diversified fund might be.</p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0"> The Fund is not a complete
investment program and you may lose money by investing in the Fund. </p>
<p style="font: 10pt Times New Roman, Times, Serif; margin: 5.6pt 0">An investment
in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other
government agency, entity or person. </p>
EVBAX
EVBIX
Reflects the Fund's allocable share of the advisory fee and other expenses of the Portfolios in which it invests.
The investment adviser and administrator have agreed to reimburse the Fund's expenses to the extent that Total Annual Fund Operating Expenses exceed 0.95% for Class A shares and 0.70% for Class I shares. This expense reimbursement will continue through February 28, 2014. Any amendment to or a termination of this reimbursement would require written approval of the Board of Trustees. The expense reimbursement relates to ordinary operating expenses only and does not include expenses such as: brokerage commissions, acquired fund fees and expenses, interest expense, taxes or litigation expenses. Amounts reimbursed may be recouped by the investment adviser and administrator during the Fund's current fiscal year to the extent actual expenses are less than the contractual expense cap during such year.