497

Eaton Vance Management

Two International Place

Boston, MA 02110

(617)482-8260

www.eatonvance.com

June 29, 2018

Securities and Exchange Commission

100 F Street, NE

Washington, DC 20549

Attn: Office of Filings, Information & Consumer Services

Re: Eaton Vance Special Investment Trust (the “Registrant”) (1933 Act File No. 002-27962) on behalf of Eaton Vance Multisector Income Fund (the “Fund”)

Ladies and Gentlemen:

On behalf of the Registrant and pursuant to Rule 497(e) under the Securities Act of 1933, as amended, attached for filing is an exhibit containing interactive data format risk/return summary information that mirrors the risk/return summary information in a Prospectus dated March 1, 2018 as revised June 25, 2018. The purpose of the filing is to submit the 497(e) filing dated June 25, 2018 in XBRL for the Fund.

Please contact me at (617) 672-6548 if you have any questions or comments.

Very truly yours,

/s/ Courtney Gramstorff

Courtney Gramstorff

XML

Document and Entity Information	Total
Risk/Return:
Document Type	497
Document Period End Date	Oct. 31, 2017
Registrant Name	EATON VANCE SPECIAL INVESTMENT TRUST
Central Index Key	0000031266
Amendment Flag	false
Document Creation Date	Jun. 25, 2018
Document Effective Date	Jun. 25, 2018
Prospectus Date	Mar. 01, 2018
Eaton Vance Multisector Income Fund | Class A
Risk/Return:
Trading Symbol	EVBAX
Eaton Vance Multisector Income Fund | Class C
Risk/Return:
Trading Symbol	EVBCX
Eaton Vance Multisector Income Fund | Class I
Risk/Return:
Trading Symbol	EVBIX
Eaton Vance Multisector Income Fund | Class R
Risk/Return:
Trading Symbol	EVBRX
Eaton Vance Multisector Income Fund | Class R6
Risk/Return:
Trading Symbol	EVBSX

XML

Eaton Vance Multisector Income Fund

Investment Objective

The Fund’s investment objective is total return.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Investors may also pay commissions or other fees to their financial intermediary when they buy and hold shares of the Fund, which are not reflected below. You may qualify for a reduced sales charge on purchases of Class A shares if you invest, or agree to invest over a 13-month period, at least $50,000 in Eaton Vance funds. Certain financial intermediaries also may offer variations in Fund sales charges to their customers as described in Appendix A – Financial Intermediary Sales Charge Variations in this Prospectus. More information about these and other discounts is available from your financial intermediary and in Sales Charges beginning on page 28 of this Prospectus and page 20 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - Eaton Vance Multisector Income Fund	Class A	Class C	Class I	Class R	Class R6
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%	none	none	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of the lower of net asset value at purchase or redemption)	none	1.00%	none	none	none

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

Annual Fund Operating Expenses - Eaton Vance Multisector Income Fund		Class A	Class C	Class I	Class R	Class R6
Management Fees		0.55%	0.55%	0.55%	0.55%	0.55%
Distribution and Service (12b-1) Fees		0.25%	1.00%	none	0.50%	none
Other Expenses	[1]	0.16%	0.16%	0.16%	0.16%	0.10%
Total Annual Fund Operating Expenses		0.96%	1.71%	0.71%	1.21%	0.65%

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 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 and that any expense reimbursement arrangement remains in place for the contractual period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - Eaton Vance Multisector Income Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	568	766	981	1,597
Class C	274	539	928	2,019
Class I	73	227	395	883
Class R	123	384	665	1,466
Class R6	66	208	362	810

Expense Example, No Redemption - Eaton Vance Multisector Income Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	568	766	981	1,597
Class C	174	539	928	2,019
Class I	73	227	395	883
Class R	123	384	665	1,466
Class R6	66	208	362	810

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells 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. During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 44% of the average value of its portfolio.

Principal Investment Strategies

Under normal market conditions, the Fund invests at least 80% of its net assets (plus any borrowings for investment purposes) 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 and collateralized mortgage obligations) and other asset-backed securities (including collateralized debt obligations), zero-coupon securities, when-issued securities, forward commitments, repurchase agreements, reverse repurchase agreements, foreign debt securities (including those issued by companies domiciled in emerging market countries), sovereign debt (including debt issued by emerging market countries), obligations of supranational entities, structured notes, municipal obligations, private placements, inflation-indexed bonds and convertible securities and other hybrid securities (other than preferred stock). 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 S&P Global Ratings (“S&P”) or by Fitch Ratings (“Fitch”) or lower than Baa by Moody’s Investors Service, Inc. (“Moody’s”)) and in unrated instruments determined by the investment adviser to be of below investment grade quality (“junk”) (the “35% Policy”). For purposes of rating restrictions, if securities are rated differently by two or more rating agencies, the highest rating is used. Total return is defined as income plus capital appreciation. 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 preferred stock and equity securities of smaller and mid-sized companies, publicly-traded real estate investment trusts (“REITs”) and foreign equity securities. The Fund may engage in derivatives transactions, including futures contracts, options contracts, forward foreign currency exchange contracts, credit-linked notes, interest rate swaps, total return swaps, inflation swaps, credit default swaps and swaptions. The Fund expects to principally use derivatives to hedge against fluctuations in currency exchange rates and to manage interest rate and credit risk or otherwise for investment purposes. The market value of derivatives that have characteristics similar to bonds or other income instruments will be included with bonds and other income instruments for purposes of the Fund’s 80% Policy and 35% Policy. There is no stated limit on the Fund’s use of derivatives. The Fund may hold cash and may invest in money market instruments. 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.

In managing the Fund, the investment adviser employs a bottom-up, research-driven and value-oriented approach that generally seeks to identify pricing anomalies that occur due to both technical and fundamental factors, including 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. In selecting securities, the investment adviser generally seeks issuers with attractive valuations and improving fundamentals. The portfolio managers have broad discretion to invest across asset classes, sectors and geographies and the Fund may at times have significant exposure to a specific asset class, sector or region. The investment adviser may sell a security when the investment adviser’s price objective for the security is reached, the fundamentals of the company deteriorate or to pursue more attractive investment options. The investment adviser also considers how purchasing or selling an investment would impact the overall portfolio’s potential return (income and capital gains) and risk profile (for example, its sensitivity to currency risk, interest rate risk and sector-specific risk) on both a benchmark-relative and absolute return basis, and may include allocations to securities outside the benchmark. 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. The Fund’s returns are expected to be more volatile than those of its benchmark.

Principal Risks

Market Risk. The value of investments held by the Fund may increase or decrease in response to economic, political and financial events (whether real, expected or perceived) in the U.S. and global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in reaction to changing market conditions. Actions taken by the U.S. Federal Reserve or foreign central banks to stimulate or stabilize economic growth, such as decreases or increases in short-term interest rates, could cause high volatility in markets. No active trading market may exist for certain investments, which may impair the ability of the Fund to sell or to realize the current valuation of such investments in the event of the need to liquidate such assets. Fixed-income markets may experience periods of relatively high volatility in an environment where U.S. treasury yields are rising.

Credit Risk. Investments in bonds and other income instruments, including loans (referred to below as “debt instruments”) 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 debt instruments also may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, 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, which may increase the Fund’s operating expenses and adversely affect net asset value.

Interest Rate Risk. In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise. Generally, securities with longer maturities are more sensitive to changes in interest rates than shorter maturity securities, causing them to be more volatile. Conversely, fixed income securities with shorter maturities will be less volatile but generally provide lower returns than fixed income securities with longer maturities. In a rising interest rate environment, the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate.

Lower Rated Investments Risk. Investments rated below investment grade and comparable unrated investments (sometimes referred to as “junk”) 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.

Additional Risks of Loans. Loans are traded in a private, unregulated inter-dealer or inter-bank resale market and are generally subject to contractual restrictions that must be satisfied before a loan can be bought or sold. These restrictions may impede the Fund’s ability to buy or sell loans (thus affecting their liquidity) and may negatively impact the transaction price. See also “Market Risk” above. It also may take longer than seven days for transactions in loans to settle. Due to the possibility of an extended loan settlement process, the Fund may hold cash, sell investments or temporarily borrow from banks or other lenders to meet short-term liquidity needs, such as to satisfy redemption requests from Fund shareholders. Loans may be structured such that they are not securities under securities law, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. Loans are also subject to risks associated with other types of income investments as described herein.

U.S. Government Securities Risk. 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. U.S. Treasury securities generally have a lower return than other obligations because of their higher credit quality and market liquidity.

Mortgage- and Asset-Backed Securities Risk. Mortgage- and asset-backed securities represent interests in “pools” of commercial or residential mortgages or other assets, including consumer loans or receivables. Movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain types of mortgage- and asset-backed securities. Although certain mortgage- and asset-backed securities are guaranteed as to timely payment of interest and principal by a government entity, the market price for such securities is not guaranteed and will fluctuate. The purchase of mortgage- and asset-backed securities issued by non-government entities may entail greater risk than such securities that are issued or guaranteed by a government entity. Mortgage- and asset-backed securities issued by non-government entities may offer higher yields than those issued by government entities, but may also be subject to greater volatility than government issues and can also be subject to greater credit risk and the risk of default on the underlying mortgages or other assets. Investments in mortgage- and asset-backed securities are subject to both extension risk, where borrowers pay off their debt obligations more slowly in times of rising interest rates, and prepayment risk, where borrowers pay off their debt obligations sooner than expected in times of declining interest rates.

Money Market Instrument Risk. Money market instruments may be adversely affected by market and economic events, such as a sharp rise in prevailing short-term interest rates; adverse developments in the banking industry, which issues or guarantees many money market instruments; adverse economic, political or other developments affecting issuers of money market instruments; changes in the credit quality of issuers; and default by a counterparty.

Zero-Coupon Bond Risk. Zero-coupon bonds may experience greater volatility in market value due to changes in interest rates. The Fund accrues income on the discount amortization of these investments, which it is required to distribute each year. The Fund may be required to sell investments to obtain cash needed for income distributions.

When-Issued and Forward Commitment Risk. Securities purchased on a when-issued or forward commitment basis are subject to the risk that when delivered they will be worth less than the agreed upon payment price.

Risks of Repurchase Agreements and Reverse Repurchase Agreements. In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. In a repurchase agreement, such insolvency 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 equal to the repurchase price. In a reverse repurchase agreement, the counterparty’s insolvency may result in a loss equal to the amount by which the value of the securities sold by the Fund exceeds the repurchase price payable by the Fund; if the value of the purchased securities increases during such a delay, that loss may also be increased. When the Fund enters into a reverse repurchase agreement, any fluctuations in the market value of either the securities sold to the counterparty or the securities which the Fund purchases with its proceeds from the agreement would affect the value of the Fund’s assets. As a result, such agreements may increase fluctuations in the net asset value of the Fund’s shares. Because reverse repurchase agreements may be considered to be a form of borrowing by the Fund (and a loan from the counterparty), they constitute leverage. If the Fund reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

Foreign Investment Risk. Foreign investments can be adversely affected by political, economic and market developments abroad, including the imposition of economic and other sanctions by the United States or another country. Foreign markets may be smaller, less liquid and more volatile than the major markets in the United States, and as a result, Fund share values may be more volatile. Trading in foreign 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.

Economic data as reported by sovereign entities may be delayed, inaccurate or fraudulent. In the event of a default by a sovereign entity, there are typically no assets to be seized or cash flows to be attached. Furthermore, the willingness or ability of a sovereign entity to renegotiate defaulted debt may be limited. Therefore, losses on sovereign defaults may far exceed the losses from the default of a similarly rated U.S. debt issuer.

Emerging Markets Investment Risk. Investment markets in emerging market countries are typically smaller, less liquid and more volatile than developed markets, and emerging market securities often involve greater risks than developed market securities.

Currency Risk. Exchange rates for currencies fluctuate daily. The value of foreign investments may be affected favorably or unfavorably by changes in currency exchange rates in relation to the U.S. dollar. Currency markets generally are not as regulated as securities markets and currency transactions are subject to settlement, custodial and other operational risks.

Municipal Obligation Risk. The amount of public information available about municipal obligations is generally less than for corporate equities or bonds, meaning that the investment performance of municipal obligations may be more dependent on the analytical abilities of the investment adviser than stock or corporate bond investments. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund’s ability to sell its municipal obligations at attractive prices. The differences between the price at which an obligation can be purchased and the price at which it can be sold may widen during periods of market distress. Less liquid obligations can become more difficult to value and be subject to erratic price movements. The increased presence of nontraditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume.

Inflation-Linked Investments Risk. Inflation-linked investments are subject to the effects of changes in market interest rates caused by factors other than inflation (real interest rates). In general, the price of an inflation-linked investment tends to decrease when real interest rates increase and increase when real interest rates decrease. Interest payments on inflation-linked investments may vary widely and will fluctuate as the principal and interest are adjusted for inflation. Any increase in the principal amount of an inflation-linked investment will be considered taxable ordinary income, even though the Fund will not receive the principal until maturity. There can be no assurance that the inflation index used will accurately measure the real rate of inflation in the prices of goods and services. The Fund’s investments in inflation-linked investments may lose value in the event that the actual rate of inflation is different from the rate of the inflation index.

Convertible and Other Hybrid Securities Risk. Convertible and other hybrid securities generally possess characteristics common to both equity and debt securities. In addition to risks associated with investing in income securities, such as interest rate and credit risks, convertible and other hybrid securities may be subject to issuer-specific and market risks generally applicable to equity securities. Convertible securities may also react to changes in the value of the common stock into which they convert, and are thus subject to equity investing and market risks. A convertible security may be converted at an inopportune time, which may decrease the Fund’s return.

Equity Securities Risk. The value of equity securities and related instruments may decline in response to adverse changes in the economy or the economic outlook; deterioration in investor sentiment; interest rate, currency, and commodity price fluctuations; adverse geopolitical, social or environmental developments; issuer and sector-specific considerations; and other factors. Market conditions may affect certain types of stocks to a greater extent than other types of stocks. If the stock market declines in value, the value of the Fund’s equity securities will also likely decline. Although prices can rebound, there is no assurance that values will return to previous levels.

Smaller Company Risk. The stocks of smaller and mid-sized companies are generally subject to greater price fluctuations, limited liquidity, higher transaction costs and higher investment risk than the stocks of larger, more established companies. Such companies may have limited product lines, markets or financial resources, may be dependent on a limited management group, and may lack substantial capital reserves or an established performance record. There may be generally less publicly available information about such companies than for larger, more established companies. Stocks of these companies frequently have lower trading volumes making them more volatile and potentially more difficult to value.

Preferred Stock Risk. Although preferred stocks represent an ownership interest in an issuer, preferred stocks generally do not have voting rights or have limited voting rights and have economic characteristics similar to fixed-income securities. Preferred stocks are subject to issuer-specific risks generally applicable to equity securities and credit and interest rate risks generally applicable to fixed-income securities. The value of preferred stock generally declines when interest rates rise and may react more significantly than bonds and other debt instruments to actual or perceived changes in the company’s financial condition or prospects.

Real Estate Risk. Real estate investments are subject to risks associated with owning real estate, including declines in real estate values, increases in property taxes, fluctuations in interest rates, limited availability of mortgage financing, decreases in revenues from underlying real estate assets, declines in occupancy rates, changes in government regulations affecting zoning, land use, and rents, environmental liabilities, and risks related to 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. REITs must satisfy specific requirements for favorable tax treatment and can involve unique risks in addition to the risks generally affecting the real estate industry. Changes in underlying real estate values may have an exaggerated effect to the extent that investments are concentrated in particular geographic regions or property types.

Derivatives Risk. The Fund’s exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. 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 leverage in the Fund, which represents a non-cash exposure to the underlying asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Fund. 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. Use of 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. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying asset, rate, index or instrument. Derivative instruments traded in over-the-counter markets 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, particularly when there is no stated limit on the Fund’s use of derivatives. A derivative investment also involves the risks relating to the asset, index, rate or instrument underlying the investment.

Leverage Risk. Certain fund transactions may give rise to leverage. Leverage can result from a non-cash exposure to an asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Fund. 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’s share price 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 investments may substantially exceed the initial investment.

Restricted and Illiquid Securities Risk. Unless registered for sale to the public under applicable federal securities law, restricted securities can be sold only in private transactions to qualified purchasers pursuant to an exemption from registration. The sale price realized from a private transaction could be less than the Fund’s purchase price for the restricted security. It may be difficult to identify a qualified purchaser for a restricted security held by the Fund and such security could be deemed illiquid. The Fund may not invest more than 15% of its net assets in illiquid securities, which may be difficult to value properly and may involve greater risks than liquid securities. Restricted securities may also be difficult to value.

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 a fund that is “diversified.” Non-diversified funds may focus their investments in a small number of issuers, making them more susceptible to risks affecting such issuers than a more diversified fund might be.

Sector Risk. Because the Fund may invest a significant portion of its assets in a specific asset class, sector or region, the value of Fund shares may be affected by events that adversely affect a state, U.S. territory, sector or type of obligation and may fluctuate more than that of a fund that invests more broadly.

Risks Associated with Active Management. The success of the Fund’s investment strategy depends on portfolio management’s successful application of analytical skills and investment judgment. Active management involves subjective decisions.

General Fund Investing Risks. The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objective. It is possible to lose money by investing in the Fund. The Fund is designed to be a long-term investment vehicle and is not suited for short-term trading. Investors in the Fund should have a long-term investment perspective and be able to tolerate potentially sharp declines in value. 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. 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.

Performance

The following bar chart and table provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and how the Fund’s average annual returns over time compare with those of a broad-based securities market index and a blended index. The returns in the bar chart are for Class A shares and do not reflect a sales charge. If the sales charge was reflected, the returns would be lower. Past performance (both before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The Fund’s performance for certain periods reflects the effects of expense reductions. Absent these reductions, performance for certain periods would have been lower. Updated Fund performance information can be obtained by visiting www.eatonvance.com.

During the period from December 31, 2013 to December 31, 2017, the highest quarterly total return for Class A was 6.74% for the quarter ended June 30, 2016, and the lowest quarterly return was -12.54% for the quarter ended September 30, 2015. For the 30 days ended October 31, 2017, the SEC yield for Class A shares was 3.06%, for Class C shares was 2.46%, for Class I shares was 3.47%, for Class R shares was 2.97% and for Class R6 shares was 3.51%. Current yield information can be obtained by visiting www.eatonvance.com.

Average Annual Total Return as of December 31, 2017

Average Annual Total Returns - Eaton Vance Multisector Income Fund		One Year	Life of Fund	Inception Date
Class A		5.37%	4.08%	Jan. 31, 2013
Class A | After Taxes on Distributions		3.93%	2.88%
Class A | After Taxes on Distributions and Sales		3.15%	2.69%
Class C		8.84%	4.43%	Aug. 20, 2013
Class I		10.82%	5.37%	Jan. 31, 2013
Class R		10.29%	4.93%	Nov. 12, 2014
Class R6		10.98%	5.43%	Nov. 12, 2014
Bloomberg Barclays U.S. Government/Credit Bond Index (reflects no deduction for fees, expenses or taxes)		4.00%	2.33%
ICE BofAML U.S. High Yield Index (reflects no deduction for fees, expenses or taxes)		7.48%	5.61%
Blended Index (reflects no deduction for fees, expenses or taxes)	[1]	5.21%	3.50%

These returns reflect the maximum sales charge for Class A (4.75%) and any applicable contingent deferred sales charge (“CDSC”) for Class C. Class A and Class I commenced operations on January 31, 2013. The Class C and Class R performance shown above for the periods prior to August 20, 2013 and November 12, 2014 (commencement of operations for each class, respectively) is the performance of Class A shares at net asset value without adjustment for any differences in the expenses of the classes. The Class R6 performance shown above for the period prior to November 12, 2014 (commencement of operations) is the performance of Class I shares at net asset value without adjustment for any differences in the expenses of the two classes. If adjusted for such differences, returns would be different. ICE Data Indices, LLC indices not for redistribution or other uses; provided “as is,” without warranties, and with no liability. Eaton Vance has prepared this report, ICE Data Indices, LLC does not endorse it, or guarantee, review, or endorse Eaton Vance’s products. Investors cannot invest directly in an Index.

After-tax returns are calculated using the highest historical individual federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on a shareholder’s tax situation and the actual characterization of distributions, and may differ from those shown. After-tax returns are not relevant to shareholders who hold shares in tax-deferred accounts or to shares held by non-taxable entities. After-tax returns for other Classes of shares will vary from the after-tax returns presented for Class A shares. Return After Taxes on Distributions for a period may be the same as Return Before Taxes for that period because no taxable distributions were made during that period. Also, Return After Taxes on Distributions and the Sale of Fund Shares for a period may be greater than or equal to Return After Taxes on Distributions for the same period because of losses realized on the sale of Fund shares.

[1] Other Expenses have been restated to delete the fees allocated to the Fund in connection with investing in Multisector Income Portfolio (the "Portfolio"), the Fund's former master portfolio.

[1] The Blended Index consists of 65% Bloomberg Barclays U.S. Government/Credit Bond Index and 35% ICE BofAML U.S. High Yield Index, rebalanced monthly.

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Risk/Return:

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Eaton Vance Multisector Income Fund

Risk/Return:

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Investment Objective, Heading

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Investment Objective

Investment Objective, Primary

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The Fund’s investment objective is total return.

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Fees and Expenses of the Fund

Expense, Narrative

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This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Investors may also pay commissions or other fees to their financial intermediary when they buy and hold shares of the Fund, which are not reflected below. You may qualify for a reduced sales charge on purchases of Class A shares if you invest, or agree to invest over a 13-month period, at least $50,000 in Eaton Vance funds. Certain financial intermediaries also may offer variations in Fund sales charges to their customers as described in Appendix A – Financial Intermediary Sales Charge Variations in this Prospectus. More information about these and other discounts is available from your financial intermediary and in Sales Charges beginning on page 28 of this Prospectus and page 20 of the Fund’s Statement of Additional Information.

Shareholder Fees, Caption

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Shareholder Fees (fees paid directly from your investment)

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

Portfolio Turnover, Heading

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Portfolio Turnover

Portfolio Turnover

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The Fund pays transaction costs, such as commissions, when it buys and sells 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. During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 44% of the average value of its portfolio.

Portfolio Turnover, Rate

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44.00%

Expense Breakpoint, Discounts

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You may qualify for a reduced sales charge on purchases of Class A shares if you invest, or agree to invest over a 13-month period, at least $50,000 in Eaton Vance funds. Certain financial intermediaries also may offer variations in Fund sales charges to their customers as described in Appendix A - Financial Intermediary Sales Charge Variations in this Prospectus. More information about these and other discounts is available from your financial intermediary and in Sales Charges beginning on page 28 of this Prospectus and page 20 of the Fund's Statement of Additional Information.

Expense Breakpoint, Minimum Investment Required Amount

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$ 50,000

Expenses Restated to Reflect Current

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Other Expenses have been restated to delete the fees allocated to the Fund in connection with investing in Multisector Income Portfolio (the “Portfolio”), the Fund’s former master portfolio.

Expense Example, Heading

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Example.

Expense Example, Narrative

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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 and that any expense reimbursement arrangement remains in place for the contractual period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Investment Strategy, Heading

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Principal Investment Strategies

Investment Strategy, Narrative

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Under normal market conditions, the Fund invests at least 80% of its net assets (plus any borrowings for investment purposes) 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 and collateralized mortgage obligations) and other asset-backed securities (including collateralized debt obligations), zero-coupon securities, when-issued securities, forward commitments, repurchase agreements, reverse repurchase agreements, foreign debt securities (including those issued by companies domiciled in emerging market countries), sovereign debt (including debt issued by emerging market countries), obligations of supranational entities, structured notes, municipal obligations, private placements, inflation-indexed bonds and convertible securities and other hybrid securities (other than preferred stock). 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 S&P Global Ratings (“S&P”) or by Fitch Ratings (“Fitch”) or lower than Baa by Moody’s Investors Service, Inc. (“Moody’s”)) and in unrated instruments determined by the investment adviser to be of below investment grade quality (“junk”) (the “35% Policy”). For purposes of rating restrictions, if securities are rated differently by two or more rating agencies, the highest rating is used. Total return is defined as income plus capital appreciation. 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 preferred stock and equity securities of smaller and mid-sized companies, publicly-traded real estate investment trusts (“REITs”) and foreign equity securities. The Fund may engage in derivatives transactions, including futures contracts, options contracts, forward foreign currency exchange contracts, credit-linked notes, interest rate swaps, total return swaps, inflation swaps, credit default swaps and swaptions. The Fund expects to principally use derivatives to hedge against fluctuations in currency exchange rates and to manage interest rate and credit risk or otherwise for investment purposes. The market value of derivatives that have characteristics similar to bonds or other income instruments will be included with bonds and other income instruments for purposes of the Fund’s 80% Policy and 35% Policy. There is no stated limit on the Fund’s use of derivatives. The Fund may hold cash and may invest in money market instruments. 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.

In managing the Fund, the investment adviser employs a bottom-up, research-driven and value-oriented approach that generally seeks to identify pricing anomalies that occur due to both technical and fundamental factors, including 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. In selecting securities, the investment adviser generally seeks issuers with attractive valuations and improving fundamentals. The portfolio managers have broad discretion to invest across asset classes, sectors and geographies and the Fund may at times have significant exposure to a specific asset class, sector or region. The investment adviser may sell a security when the investment adviser’s price objective for the security is reached, the fundamentals of the company deteriorate or to pursue more attractive investment options. The investment adviser also considers how purchasing or selling an investment would impact the overall portfolio’s potential return (income and capital gains) and risk profile (for example, its sensitivity to currency risk, interest rate risk and sector-specific risk) on both a benchmark-relative and absolute return basis, and may include allocations to securities outside the benchmark. 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. The Fund’s returns are expected to be more volatile than those of its benchmark.

Strategy Portfolio Concentration

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Under normal market conditions, the Fund invests at least 80% of its net assets (plus any borrowings for investment purposes) 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 and collateralized mortgage obligations) and other asset-backed securities (including collateralized debt obligations), zero-coupon securities, when-issued securities, forward commitments, repurchase agreements, reverse repurchase agreements, foreign debt securities (including those issued by companies domiciled in emerging market countries), sovereign debt (including debt issued by emerging market countries), obligations of supranational entities, structured notes, municipal obligations, private placements, inflation-indexed bonds and convertible securities and other hybrid securities (other than preferred stock). 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 S&P Global Ratings (“S&P”) or by Fitch Ratings (“Fitch”) or lower than Baa by Moody’s Investors Service, Inc. (“Moody’s”)) and in unrated instruments determined by the investment adviser to be of below investment grade quality (“junk”) (the “35% Policy”). For purposes of rating restrictions, if securities are rated differently by two or more rating agencies, the highest rating is used. Total return is defined as income plus capital appreciation. 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 preferred stock and equity securities of smaller and mid-sized companies, publicly-traded real estate investment trusts (“REITs”) and foreign equity securities. The Fund may engage in derivatives transactions, including futures contracts, options contracts, forward foreign currency exchange contracts, credit-linked notes, interest rate swaps, total return swaps, inflation swaps, credit default swaps and swaptions. The Fund expects to principally use derivatives to hedge against fluctuations in currency exchange rates and to manage interest rate and credit risk or otherwise for investment purposes. The market value of derivatives that have characteristics similar to bonds or other income instruments will be included with bonds and other income instruments for purposes of the Fund’s 80% Policy and 35% Policy. There is no stated limit on the Fund’s use of derivatives. The Fund may hold cash and may invest in money market instruments. 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.

Risk, Heading

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Principal Risks

Risk, Narrative

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Market Risk. The value of investments held by the Fund may increase or decrease in response to economic, political and financial events (whether real, expected or perceived) in the U.S. and global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in reaction to changing market conditions. Actions taken by the U.S. Federal Reserve or foreign central banks to stimulate or stabilize economic growth, such as decreases or increases in short-term interest rates, could cause high volatility in markets. No active trading market may exist for certain investments, which may impair the ability of the Fund to sell or to realize the current valuation of such investments in the event of the need to liquidate such assets. Fixed-income markets may experience periods of relatively high volatility in an environment where U.S. treasury yields are rising.

Credit Risk. Investments in bonds and other income instruments, including loans (referred to below as “debt instruments”) 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 debt instruments also may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, 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, which may increase the Fund’s operating expenses and adversely affect net asset value.

Interest Rate Risk. In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise. Generally, securities with longer maturities are more sensitive to changes in interest rates than shorter maturity securities, causing them to be more volatile. Conversely, fixed income securities with shorter maturities will be less volatile but generally provide lower returns than fixed income securities with longer maturities. In a rising interest rate environment, the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate.

Lower Rated Investments Risk. Investments rated below investment grade and comparable unrated investments (sometimes referred to as “junk”) 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.

Additional Risks of Loans. Loans are traded in a private, unregulated inter-dealer or inter-bank resale market and are generally subject to contractual restrictions that must be satisfied before a loan can be bought or sold. These restrictions may impede the Fund’s ability to buy or sell loans (thus affecting their liquidity) and may negatively impact the transaction price. See also “Market Risk” above. It also may take longer than seven days for transactions in loans to settle. Due to the possibility of an extended loan settlement process, the Fund may hold cash, sell investments or temporarily borrow from banks or other lenders to meet short-term liquidity needs, such as to satisfy redemption requests from Fund shareholders. Loans may be structured such that they are not securities under securities law, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. Loans are also subject to risks associated with other types of income investments as described herein.

U.S. Government Securities Risk. 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. U.S. Treasury securities generally have a lower return than other obligations because of their higher credit quality and market liquidity.

Mortgage- and Asset-Backed Securities Risk. Mortgage- and asset-backed securities represent interests in “pools” of commercial or residential mortgages or other assets, including consumer loans or receivables. Movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain types of mortgage- and asset-backed securities. Although certain mortgage- and asset-backed securities are guaranteed as to timely payment of interest and principal by a government entity, the market price for such securities is not guaranteed and will fluctuate. The purchase of mortgage- and asset-backed securities issued by non-government entities may entail greater risk than such securities that are issued or guaranteed by a government entity. Mortgage- and asset-backed securities issued by non-government entities may offer higher yields than those issued by government entities, but may also be subject to greater volatility than government issues and can also be subject to greater credit risk and the risk of default on the underlying mortgages or other assets. Investments in mortgage- and asset-backed securities are subject to both extension risk, where borrowers pay off their debt obligations more slowly in times of rising interest rates, and prepayment risk, where borrowers pay off their debt obligations sooner than expected in times of declining interest rates.

Money Market Instrument Risk. Money market instruments may be adversely affected by market and economic events, such as a sharp rise in prevailing short-term interest rates; adverse developments in the banking industry, which issues or guarantees many money market instruments; adverse economic, political or other developments affecting issuers of money market instruments; changes in the credit quality of issuers; and default by a counterparty.

Zero-Coupon Bond Risk. Zero-coupon bonds may experience greater volatility in market value due to changes in interest rates. The Fund accrues income on the discount amortization of these investments, which it is required to distribute each year. The Fund may be required to sell investments to obtain cash needed for income distributions.

When-Issued and Forward Commitment Risk. Securities purchased on a when-issued or forward commitment basis are subject to the risk that when delivered they will be worth less than the agreed upon payment price.

Risks of Repurchase Agreements and Reverse Repurchase Agreements. In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. In a repurchase agreement, such insolvency 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 equal to the repurchase price. In a reverse repurchase agreement, the counterparty’s insolvency may result in a loss equal to the amount by which the value of the securities sold by the Fund exceeds the repurchase price payable by the Fund; if the value of the purchased securities increases during such a delay, that loss may also be increased. When the Fund enters into a reverse repurchase agreement, any fluctuations in the market value of either the securities sold to the counterparty or the securities which the Fund purchases with its proceeds from the agreement would affect the value of the Fund’s assets. As a result, such agreements may increase fluctuations in the net asset value of the Fund’s shares. Because reverse repurchase agreements may be considered to be a form of borrowing by the Fund (and a loan from the counterparty), they constitute leverage. If the Fund reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

Foreign Investment Risk. Foreign investments can be adversely affected by political, economic and market developments abroad, including the imposition of economic and other sanctions by the United States or another country. Foreign markets may be smaller, less liquid and more volatile than the major markets in the United States, and as a result, Fund share values may be more volatile. Trading in foreign 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.

Economic data as reported by sovereign entities may be delayed, inaccurate or fraudulent. In the event of a default by a sovereign entity, there are typically no assets to be seized or cash flows to be attached. Furthermore, the willingness or ability of a sovereign entity to renegotiate defaulted debt may be limited. Therefore, losses on sovereign defaults may far exceed the losses from the default of a similarly rated U.S. debt issuer.

Emerging Markets Investment Risk. Investment markets in emerging market countries are typically smaller, less liquid and more volatile than developed markets, and emerging market securities often involve greater risks than developed market securities.

Currency Risk. Exchange rates for currencies fluctuate daily. The value of foreign investments may be affected favorably or unfavorably by changes in currency exchange rates in relation to the U.S. dollar. Currency markets generally are not as regulated as securities markets and currency transactions are subject to settlement, custodial and other operational risks.

Municipal Obligation Risk. The amount of public information available about municipal obligations is generally less than for corporate equities or bonds, meaning that the investment performance of municipal obligations may be more dependent on the analytical abilities of the investment adviser than stock or corporate bond investments. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund’s ability to sell its municipal obligations at attractive prices. The differences between the price at which an obligation can be purchased and the price at which it can be sold may widen during periods of market distress. Less liquid obligations can become more difficult to value and be subject to erratic price movements. The increased presence of nontraditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume.

Inflation-Linked Investments Risk. Inflation-linked investments are subject to the effects of changes in market interest rates caused by factors other than inflation (real interest rates). In general, the price of an inflation-linked investment tends to decrease when real interest rates increase and increase when real interest rates decrease. Interest payments on inflation-linked investments may vary widely and will fluctuate as the principal and interest are adjusted for inflation. Any increase in the principal amount of an inflation-linked investment will be considered taxable ordinary income, even though the Fund will not receive the principal until maturity. There can be no assurance that the inflation index used will accurately measure the real rate of inflation in the prices of goods and services. The Fund’s investments in inflation-linked investments may lose value in the event that the actual rate of inflation is different from the rate of the inflation index.

Convertible and Other Hybrid Securities Risk. Convertible and other hybrid securities generally possess characteristics common to both equity and debt securities. In addition to risks associated with investing in income securities, such as interest rate and credit risks, convertible and other hybrid securities may be subject to issuer-specific and market risks generally applicable to equity securities. Convertible securities may also react to changes in the value of the common stock into which they convert, and are thus subject to equity investing and market risks. A convertible security may be converted at an inopportune time, which may decrease the Fund’s return.

Equity Securities Risk. The value of equity securities and related instruments may decline in response to adverse changes in the economy or the economic outlook; deterioration in investor sentiment; interest rate, currency, and commodity price fluctuations; adverse geopolitical, social or environmental developments; issuer and sector-specific considerations; and other factors. Market conditions may affect certain types of stocks to a greater extent than other types of stocks. If the stock market declines in value, the value of the Fund’s equity securities will also likely decline. Although prices can rebound, there is no assurance that values will return to previous levels.

Smaller Company Risk. The stocks of smaller and mid-sized companies are generally subject to greater price fluctuations, limited liquidity, higher transaction costs and higher investment risk than the stocks of larger, more established companies. Such companies may have limited product lines, markets or financial resources, may be dependent on a limited management group, and may lack substantial capital reserves or an established performance record. There may be generally less publicly available information about such companies than for larger, more established companies. Stocks of these companies frequently have lower trading volumes making them more volatile and potentially more difficult to value.

Preferred Stock Risk. Although preferred stocks represent an ownership interest in an issuer, preferred stocks generally do not have voting rights or have limited voting rights and have economic characteristics similar to fixed-income securities. Preferred stocks are subject to issuer-specific risks generally applicable to equity securities and credit and interest rate risks generally applicable to fixed-income securities. The value of preferred stock generally declines when interest rates rise and may react more significantly than bonds and other debt instruments to actual or perceived changes in the company’s financial condition or prospects.

Real Estate Risk. Real estate investments are subject to risks associated with owning real estate, including declines in real estate values, increases in property taxes, fluctuations in interest rates, limited availability of mortgage financing, decreases in revenues from underlying real estate assets, declines in occupancy rates, changes in government regulations affecting zoning, land use, and rents, environmental liabilities, and risks related to 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. REITs must satisfy specific requirements for favorable tax treatment and can involve unique risks in addition to the risks generally affecting the real estate industry. Changes in underlying real estate values may have an exaggerated effect to the extent that investments are concentrated in particular geographic regions or property types.

Derivatives Risk. The Fund’s exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. 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 leverage in the Fund, which represents a non-cash exposure to the underlying asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Fund. 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. Use of 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. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying asset, rate, index or instrument. Derivative instruments traded in over-the-counter markets 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, particularly when there is no stated limit on the Fund’s use of derivatives. A derivative investment also involves the risks relating to the asset, index, rate or instrument underlying the investment.

Leverage Risk. Certain fund transactions may give rise to leverage. Leverage can result from a non-cash exposure to an asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Fund. 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’s share price 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 investments may substantially exceed the initial investment.

Restricted and Illiquid Securities Risk. Unless registered for sale to the public under applicable federal securities law, restricted securities can be sold only in private transactions to qualified purchasers pursuant to an exemption from registration. The sale price realized from a private transaction could be less than the Fund’s purchase price for the restricted security. It may be difficult to identify a qualified purchaser for a restricted security held by the Fund and such security could be deemed illiquid. The Fund may not invest more than 15% of its net assets in illiquid securities, which may be difficult to value properly and may involve greater risks than liquid securities. Restricted securities may also be difficult to value.

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 a fund that is “diversified.” Non-diversified funds may focus their investments in a small number of issuers, making them more susceptible to risks affecting such issuers than a more diversified fund might be.

Sector Risk. Because the Fund may invest a significant portion of its assets in a specific asset class, sector or region, the value of Fund shares may be affected by events that adversely affect a state, U.S. territory, sector or type of obligation and may fluctuate more than that of a fund that invests more broadly.

Risks Associated with Active Management. The success of the Fund’s investment strategy depends on portfolio management’s successful application of analytical skills and investment judgment. Active management involves subjective decisions.

General Fund Investing Risks. The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objective. It is possible to lose money by investing in the Fund. The Fund is designed to be a long-term investment vehicle and is not suited for short-term trading. Investors in the Fund should have a long-term investment perspective and be able to tolerate potentially sharp declines in value. 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. 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.

Risk, Lose Money

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The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objective. It is possible to lose money by investing in the Fund.

Risk, Nondiversified Status

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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 a fund that is “diversified.” Non-diversified funds may focus their investments in a small number of issuers, making them more susceptible to risks affecting such issuers than a more diversified fund might be.

Risk, Not Insured Depository Institution

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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.

Bar Chart and Performance Table, Heading

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Performance

Performance, Narrative

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The following bar chart and table provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and how the Fund’s average annual returns over time compare with those of a broad-based securities market index and a blended index. The returns in the bar chart are for Class A shares and do not reflect a sales charge. If the sales charge was reflected, the returns would be lower. Past performance (both before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The Fund’s performance for certain periods reflects the effects of expense reductions. Absent these reductions, performance for certain periods would have been lower. Updated Fund performance information can be obtained by visiting www.eatonvance.com.

Performance, Information Illustrates Variability of Returns

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The following bar chart and table provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and how the Fund’s average annual returns over time compare with those of a broad-based securities market index and a blended index.

Performance Availability Website Address

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www.eatonvance.com

Performance Past Does Not Indicate Future

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Past performance (both before and after taxes) is not necessarily an indication of how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads

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www.eatonvance.com

Bar Chart, Closing

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During the period from December 31, 2013 to December 31, 2017, the highest quarterly total return for Class A was 6.74% for the quarter ended June 30, 2016, and the lowest quarterly return was -12.54% for the quarter ended September 30, 2015. For the 30 days ended October 31, 2017, the SEC yield for Class A shares was 3.06%, for Class C shares was 2.46%, for Class I shares was 3.47%, for Class R shares was 2.97% and for Class R6 shares was 3.51%. Current yield information can be obtained by visiting www.eatonvance.com.

Highest Quarterly Return, Label

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During the period from December 31, 2013 to December 31, 2017, the highest quarterly total return for Class A was

Highest Quarterly Return, Date

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Jun. 30, 2016

Highest Quarterly Return

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6.74%

Lowest Quarterly Return, Label

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and the lowest quarterly return was

Lowest Quarterly Return, Date

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Sep. 30, 2015

Lowest Quarterly Return

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(12.54%)

Performance Table Heading

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Average Annual Total Return as of December 31, 2017

Performance Table Does Reflect Sales Loads

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These returns reflect the maximum sales charge for Class A (4.75%) and any applicable contingent deferred sales charge (“CDSC”) for Class C.

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the highest historical individual federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on a shareholder’s tax situation and the actual characterization of distributions, and may differ from those shown.

Performance Table Not Relevant to Tax Deferred

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After-tax returns are not relevant to shareholders who hold shares in tax-deferred accounts or to shares held by non-taxable entities.

Performance Table One Class of after Tax Shown

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After-tax returns for other Classes of shares will vary from the after-tax returns presented for Class A shares.

Performance Table Explanation after Tax Higher

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Return After Taxes on Distributions for a period may be the same as Return Before Taxes for that period because no taxable distributions were made during that period. Also, Return After Taxes on Distributions and the Sale of Fund Shares for a period may be greater than or equal to Return After Taxes on Distributions for the same period because of losses realized on the sale of Fund shares.

Performance Table Footnotes, Reason Performance Information for Class Different from Immediately Preceding Period [Text]

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The Class C and Class R performance shown above for the periods prior to August 20, 2013 and November 12, 2014 (commencement of operations for each class, respectively) is the performance of Class A shares at net asset value without adjustment for any differences in the expenses of the classes. The Class R6 performance shown above for the period prior to November 12, 2014 (commencement of operations) is the performance of Class I shares at net asset value without adjustment for any differences in the expenses of the two classes. If adjusted for such differences, returns would be different.

Performance Table, Closing

rr_PerformanceTableClosingTextBlock

These returns reflect the maximum sales charge for Class A (4.75%) and any applicable contingent deferred sales charge (“CDSC”) for Class C. Class A and Class I commenced operations on January 31, 2013. The Class C and Class R performance shown above for the periods prior to August 20, 2013 and November 12, 2014 (commencement of operations for each class, respectively) is the performance of Class A shares at net asset value without adjustment for any differences in the expenses of the classes. The Class R6 performance shown above for the period prior to November 12, 2014 (commencement of operations) is the performance of Class I shares at net asset value without adjustment for any differences in the expenses of the two classes. If adjusted for such differences, returns would be different. ICE Data Indices, LLC indices not for redistribution or other uses; provided “as is,” without warranties, and with no liability. Eaton Vance has prepared this report, ICE Data Indices, LLC does not endorse it, or guarantee, review, or endorse Eaton Vance’s products. Investors cannot invest directly in an Index.

After-tax returns are calculated using the highest historical individual federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on a shareholder’s tax situation and the actual characterization of distributions, and may differ from those shown. After-tax returns are not relevant to shareholders who hold shares in tax-deferred accounts or to shares held by non-taxable entities. After-tax returns for other Classes of shares will vary from the after-tax returns presented for Class A shares. Return After Taxes on Distributions for a period may be the same as Return Before Taxes for that period because no taxable distributions were made during that period. Also, Return After Taxes on Distributions and the Sale of Fund Shares for a period may be greater than or equal to Return After Taxes on Distributions for the same period because of losses realized on the sale of Fund shares.

Eaton Vance Multisector Income Fund | Bloomberg Barclays U.S. Government/Credit Bond Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

Index No Deduction for Fees, Expenses, Taxes

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses or taxes)

One Year

rr_AverageAnnualReturnYear01

4.00%

Life of Fund

rr_AverageAnnualReturnSinceInception

2.33%

Eaton Vance Multisector Income Fund | ICE BofAML U.S. High Yield Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

Index No Deduction for Fees, Expenses, Taxes

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses or taxes)

One Year

rr_AverageAnnualReturnYear01

7.48%

Life of Fund

rr_AverageAnnualReturnSinceInception

5.61%

Eaton Vance Multisector Income Fund | Blended Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

Index No Deduction for Fees, Expenses, Taxes

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses or taxes)

One Year

rr_AverageAnnualReturnYear01

5.21%

^[1]

Life of Fund

rr_AverageAnnualReturnSinceInception

3.50%

^[1]

Eaton Vance Multisector Income Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of the lower of net asset value at purchase or redemption)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management Fees

rr_ManagementFeesOverAssets

0.55%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.96%

1 Year

rr_ExpenseExampleYear01

$ 568

3 Years

rr_ExpenseExampleYear03

766

5 Years

rr_ExpenseExampleYear05

981

10 Years

rr_ExpenseExampleYear10

1,597

1 Year

rr_ExpenseExampleNoRedemptionYear01

568

3 Years

rr_ExpenseExampleNoRedemptionYear03

766

5 Years

rr_ExpenseExampleNoRedemptionYear05

981

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,597

Annual Return 2014

rr_AnnualReturn2014

4.69%

Annual Return 2015

rr_AnnualReturn2015

(17.24%)

Annual Return 2016

rr_AnnualReturn2016

22.13%

Annual Return 2017

rr_AnnualReturn2017

10.64%

One Year

rr_AverageAnnualReturnYear01

5.37%

Life of Fund

rr_AverageAnnualReturnSinceInception

4.08%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 31, 2013

Thirty Day Yield Column [Text]

rr_ThirtyDayYieldColumnName

For the 30 days ended October 31, 2017, the SEC yield for Class A shares was

Thirty Day Yield

rr_ThirtyDayYield

3.06%

Eaton Vance Multisector Income Fund | Class A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

3.93%

Life of Fund

rr_AverageAnnualReturnSinceInception

2.88%

Eaton Vance Multisector Income Fund | Class A | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

3.15%

Life of Fund

rr_AverageAnnualReturnSinceInception

2.69%

Eaton Vance Multisector Income Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of the lower of net asset value at purchase or redemption)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Management Fees

rr_ManagementFeesOverAssets

0.55%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.71%

1 Year

rr_ExpenseExampleYear01

$ 274

3 Years

rr_ExpenseExampleYear03

539

5 Years

rr_ExpenseExampleYear05

928

10 Years

rr_ExpenseExampleYear10

2,019

1 Year

rr_ExpenseExampleNoRedemptionYear01

174

3 Years

rr_ExpenseExampleNoRedemptionYear03

539

5 Years

rr_ExpenseExampleNoRedemptionYear05

928

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,019

One Year

rr_AverageAnnualReturnYear01

8.84%

Life of Fund

rr_AverageAnnualReturnSinceInception

4.43%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 20, 2013

Thirty Day Yield Column [Text]

rr_ThirtyDayYieldColumnName

for Class C shares was

Thirty Day Yield

rr_ThirtyDayYield

2.46%

Eaton Vance Multisector Income Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of the lower of net asset value at purchase or redemption)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management Fees

rr_ManagementFeesOverAssets

0.55%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.16%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.71%

1 Year

rr_ExpenseExampleYear01

$ 73

3 Years

rr_ExpenseExampleYear03

227

5 Years

rr_ExpenseExampleYear05

395

10 Years

rr_ExpenseExampleYear10

883

1 Year

rr_ExpenseExampleNoRedemptionYear01

73

3 Years

rr_ExpenseExampleNoRedemptionYear03

227

5 Years

rr_ExpenseExampleNoRedemptionYear05

395

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 883

One Year

rr_AverageAnnualReturnYear01

10.82%

Life of Fund

rr_AverageAnnualReturnSinceInception

5.37%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 31, 2013

Thirty Day Yield Column [Text]

rr_ThirtyDayYieldColumnName

for Class I shares was

Thirty Day Yield

rr_ThirtyDayYield

3.47%

Eaton Vance Multisector Income Fund | Class R

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of the lower of net asset value at purchase or redemption)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management Fees

rr_ManagementFeesOverAssets

0.55%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.21%

1 Year

rr_ExpenseExampleYear01

$ 123

3 Years

rr_ExpenseExampleYear03

384

5 Years

rr_ExpenseExampleYear05

665

10 Years

rr_ExpenseExampleYear10

1,466

1 Year

rr_ExpenseExampleNoRedemptionYear01

123

3 Years

rr_ExpenseExampleNoRedemptionYear03

384

5 Years

rr_ExpenseExampleNoRedemptionYear05

665

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,466

One Year

rr_AverageAnnualReturnYear01

10.29%

Life of Fund

rr_AverageAnnualReturnSinceInception

4.93%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 12, 2014

Thirty Day Yield Column [Text]

rr_ThirtyDayYieldColumnName

for Class R shares was

Thirty Day Yield

rr_ThirtyDayYield

2.97%

Eaton Vance Multisector Income Fund | Class R6

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of the lower of net asset value at purchase or redemption)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management Fees

rr_ManagementFeesOverAssets

0.55%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.10%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.65%

1 Year

rr_ExpenseExampleYear01

$ 66

3 Years

rr_ExpenseExampleYear03

208

5 Years

rr_ExpenseExampleYear05

362

10 Years

rr_ExpenseExampleYear10

810

1 Year

rr_ExpenseExampleNoRedemptionYear01

66

3 Years

rr_ExpenseExampleNoRedemptionYear03

208

5 Years

rr_ExpenseExampleNoRedemptionYear05

362

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 810

One Year

rr_AverageAnnualReturnYear01

10.98%

Life of Fund

rr_AverageAnnualReturnSinceInception

5.43%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 12, 2014

Thirty Day Yield Column [Text]

rr_ThirtyDayYieldColumnName

for Class R6 shares was

Thirty Day Yield

rr_ThirtyDayYield

3.51%

[1] The Blended Index consists of 65% Bloomberg Barclays U.S. Government/Credit Bond Index and 35% ICE BofAML U.S. High Yield Index, rebalanced monthly.

[2] Other Expenses have been restated to delete the fees allocated to the Fund in connection with investing in Multisector Income Portfolio (the "Portfolio"), the Fund's former master portfolio.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Oct. 31, 2017
Registrant Name	dei_EntityRegistrantName	EATON VANCE SPECIAL INVESTMENT TRUST
Central Index Key	dei_EntityCentralIndexKey	0000031266
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Jun. 25, 2018
Document Effective Date	dei_DocumentEffectiveDate	Jun. 25, 2018
Prospectus Date	rr_ProspectusDate	Mar. 01, 2018