ING Intermediate Bond Portfolio

INVESTMENT OBJECTIVE

The Portfolio seeks to maximize total return consistent with reasonable risk. The Portfolio seeks its objective through investments in a diversified portfolio consisting primarily of debt securities. It is anticipated that capital appreciation and investment income will both be major factors in achieving total return.

FEES AND EXPENSES OF THE PORTFOLIO

The table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. The table does not reflect fees or expenses that are, or may be, imposed under your variable annuity contracts or variable life insurance policies (“Variable Contract”) or a qualified pension or retirement plan (“Qualified Plan”). For more information on these charges, please refer to the documents governing your Variable Contract or consult your plan administrator.

The Example is intended to help you compare the cost of investing in shares of the Portfolio with the costs of investing in other mutual funds. The Example does not reflect expenses and charges which are, or may be, imposed under your Variable Contract or Qualified Plan. The Example assumes that you invest $10,000 in the Portfolio for the time periods indicated. The Example also assumes that your investment had a 5% return each year and that the Portfolio’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

The Example reflects applicable expense limitation agreements and/or waivers in effect, if any, for the one-year period and the first year of the three-, five-, and ten-year periods.

The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transactions costs. These costs, which are not reflected in Annual Portfolio Operating Expenses or in the Expense Example, affect the Portfolio’s performance.

During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 425% of the average value of its portfolio.

PRINCIPAL INVESTMENT STRATEGIES

Under normal market conditions, the Portfolio invests at least 80% of its net assets (plus borrowings for investment purposes) in a portfolio of bonds, including but not limited to corporate, government and mortgage bonds, which, at the time of purchase, are rated investment-grade ( e.g ., rated at least BBB- by Standard & Poor’s Ratings Services or Baa3 by Moody’s Investors Service, Inc.) or have an equivalent rating by a nationally recognized statistical rating organization, or are of comparable quality if unrated. The Portfolio will provide shareholders with at least 60 days’ prior notice of any change in this investment policy.

Although the Portfolio may invest a portion of its assets in high-yield (high risk) debt instruments, commonly referred to as “junk bonds,” rated below investment-grade, the Portfolio will seek to maintain a minimum average portfolio quality rating of at least investment-grade. Generally, the sub-adviser (“Sub-Adviser”) maintains a dollar-weighted average duration between three

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The Portfolio may also invest in: preferred stocks; high quality money market instruments; municipal bonds; debt instruments of foreign issuers (including those located in emerging market countries); securities denominated in foreign currencies; foreign currencies; mortgage-backed and asset-backed securities; bank loans and floating rate secured loans (“Senior Loans”); and derivatives including futures, options, and swaps involving securities, securities indices and interest rates, which may be denominated in the U.S. dollar or foreign currencies. The Portfolio typically uses derivatives to reduce exposure to other risks, such as interest rate or currency risk, to substitute for taking a position in the underlying asset, and/or to enhance returns in the Portfolio.

The Portfolio may seek to obtain exposure to the securities in which it invests by entering into a series of purchase and sale contracts or through other investment techniques such as buy backs and dollar rolls.

The Portfolio may invest in other investment companies, including exchange-traded funds, to the extent permitted under the Investment Company Act of 1940, as amended, and the rules, regulations, and exemptive orders thereunder (“1940 Act”).

The Sub-Adviser believes that relationships between the drivers of debt instrument returns change over time and that recognizing this is key to managing debt instrument assets. Therefore, the Sub-Adviser employs a dynamic investment process that balances top-down macro economic considerations and fundamental bottom-up analysis during the steps of its investment process - sector allocation, security selection, duration and yield curve management. This includes leveraging proprietary qualitative analysis along with quantitative tools throughout the portfolio construction process.

The Sub-Adviser may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into opportunities believed to be more promising, among others.

The Portfolio may lend portfolio securities on a short-term or long-term basis, up to 33¹ / ₃ % of its total assets.

PRINCIPAL RISKS

You could lose money on an investment in the Portfolio. Any of the following risks, among others, could affect Portfolio performance or cause the Portfolio to lose money or to underperform market averages of other funds.

Call   During periods of falling interest rates, a bond issuer may “call” or repay its high-yielding bond before the bond’s maturity date. If forced to invest the unanticipated proceeds at lower interest rates, the Portfolio would experience a decline in income.

Company   The price of a given company’s stock could decline or underperform for many reasons including, among others, poor management, financial problems, or business challenges. If a company declares bankruptcy or becomes insolvent, its stock could become worthless.

Credit   Prices of bonds and other debt instruments can fall if the issuer’s actual or perceived financial health deteriorates, whether because of broad economic or issuer-specific reasons. In certain cases, the issuer could be late in paying interest or principal, or could fail to pay altogether.

Currency   To the extent that the Portfolio invests directly in foreign (non-U.S.) currencies or in securities denominated in, or that trade in, foreign (non-U.S.) currencies, it is subject to the risk that those foreign (non-U.S.) currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency being hedged.

Derivative Instruments   Derivative instruments are subject to a number of risks, including the risk of changes in the market price of the underlying securities, credit risk with respect to the counterparty, risk of loss due to changes in interest rates and liquidity risk. The use of certain derivatives may also have a leveraging effect which may increase the volatility of the Portfolio and reduce its returns. Derivatives may not perform as expected, so the Portfolio may not realize the intended benefits. When used for hedging, the change in value of a derivative may not correlate as expected with the currency, security or other risk being hedged. In addition, given their complexity, derivatives expose the Portfolio to the risk of improper valuation.

Foreign Investments/Developing and Emerging Markets Investing in foreign (non-U.S.) securities may result in the Portfolio experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies due to: smaller markets; differing reporting, accounting, and auditing standards; nationalization, expropriation, or confiscatory taxation; foreign currency fluctuations, currency blockage, or replacement; potential for default on sovereign debt; or political changes or diplomatic developments. Markets and economies throughout the world are becoming increasingly interconnected, and conditions or events in one market, country or region may adversely impact investments or issuers in another market, country or region. Foreign investment risks may be greater in developing and emerging markets than in developed markets.

High-Yield Securities   Investments rated below investment-grade (or of similar quality if unrated) are known as “high-yield securities” or “junk bonds.” High-yield securities are subject to greater levels of credit and liquidity risks. High-yield securities are considered primarily speculative with respect to the issuer’s continuing ability to make principal and interest payments.

Interest in Loans   The value and the income streams of interests in loans (including participation interests in lease financings and assignments in secured variable or floating rate loans) will decline if borrowers delay payments or fail to pay altogether. A large rise in interest rates could increase this risk. Although loans are generally fully collateralized when purchased, the collateral may become illiquid or decline in value. Many loans themselves carry liquidity and valuation risks.

Interest Rate   With bonds and other fixed rate debt instruments, a rise in interest rates generally causes values to fall; conversely, values generally rise as interest rates fall. The higher the credit quality of the instrument, and the longer its maturity or duration, the more sensitive it is likely to be to interest rate risk. In the case of inverse securities, the interest rate generally will decrease when the market rate of interest to which the inverse security is indexed decreases. As of the date of this Prospectus, interest rates in the United States are at or near historic lows, which may increase the Portfolio’s exposure to risks associated with rising interest rates.

Investment Model   The manager’s proprietary model may not adequately allow for existing or unforeseen market factors or the interplay between such factors.

Liquidity   If a security is illiquid, the Portfolio might be unable to sell the security at a time when the Portfolio’s manager might wish to sell, and the security could have the effect of decreasing the overall level of the Portfolio’s liquidity. Further, the lack of an established secondary market may make it more difficult to value illiquid securities, which could vary from the amount the Portfolio could realize upon disposition. The Portfolio may make investments that become less liquid in response to market developments or adverse investor perception. The Portfolio could lose money if it cannot sell a security at the time and price that would be most beneficial to the Portfolio.

Market   Stock prices may be volatile and are affected by the real or perceived impacts of such factors as economic conditions and political events. Stock markets tend to be cyclical, with periods when stock prices generally rise and periods when stock prices generally decline. Any given stock market segment may remain out of favor with investors for a short or long period of time, and stocks as an asset class may underperform bonds or other asset classes during some periods. Additionally, legislative, regulatory or tax policies or developments in these areas may adversely impact the investment techniques available to a manager, add to Portfolio costs and impair the ability of the Portfolio to achieve its investment objectives.

Mortgage- and/or Asset-Backed Securities Defaults on or the low credit quality or liquidity of the underlying assets of the asset-backed (including mortgage-backed) securities held by the Portfolio may impair the value of the securities. There may be limitations on the enforceability of any security interest granted with respect to those underlying assets. These securities also present a higher degree of prepayment and extension risk and interest rate risk than do other types of fixed-income securities.

Municipal Obligations   The municipal market in which the Portfolio invests is volatile and can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities.

Other Investment Companies   The main risk of investing in other investment companies, including exchange-traded funds, is the risk that the value of the securities underlying an investment company might decrease. Because the Portfolio may invest in other investment companies, you will pay a proportionate share of the expenses of those other investment companies (including management fees, administration fees, and custodial fees) in addition to the expenses of the Portfolio.

Prepayment and Extension   Prepayment risk is the risk that principal on mortgages or other loan obligations underlying a security may be repaid prior to the stated maturity date, which may reduce the market value of the security and the anticipated yield-to-maturity. Extension risk is the risk that an issuer will exercise its right to repay principal on an obligation held by the Portfolio later than expected, which may decrease the value of the obligation and prevent the Portfolio from investing expected repayment proceeds in securities paying yields higher than the yields paid by the securities that were expected to be repaid.

Securities Lending   Securities lending involves two primary risks: “investment risk” and “borrower default risk.” Investment risk is the risk that the Portfolio will lose money from the investment of the cash collateral received from the borrower. Borrower default risk is the risk that the Portfolio will lose money due to the failure of a borrower to return a borrowed security in a timely manner.

U.S. Government Securities and Obligations   U.S. government securities are obligations of, or guaranteed by, the U.S. government, its agencies or government-sponsored enterprises. U.S. government securities are subject to market and interest rate risk, and may be subject to varying degrees of credit risk.

An investment in the Portfolio is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

PERFORMANCE INFORMATION

The following information is intended to help you understand the risks of investing in the Portfolio. The following bar chart shows the changes in the Portfolio’s Class S2 shares’ and Class I shares’ performance from year to year, and the table compares the Portfolio’s Class S2 shares’ and Class I shares’ performance to the performance of a broad-based securities market index/indices for the same period. Class I shares’ performance has been adjusted to reflect the higher expenses of Class S2 shares. The Class S2 shares and Class I shares of the Portfolio would have substantially similar performance because they invest in the same portfolio of securities. However, Class I shares’ performance would be

The bar chart below shows the Portfolio’s adjusted Class I shares’ performance (2003-2009) and Class S2 shares’ performance (2010-2012).

Best quarter: 3rd, 2009, 7.06% and Worst quarter: 3rd, 2008, (4.40)%

PORTFOLIO MANAGEMENT

PURCHASE AND SALE OF PORTFOLIO SHARES

Shares of the Portfolio are not offered directly to the public. Purchase and sale of shares may be made only by separate accounts of insurance companies serving as investment options under Variable Contracts or by Qualified Plans, custodian accounts, and certain investment advisers and their affiliates, other investment companies, or permitted investors. Please refer to the prospectus for the appropriate insurance company separate account, investment company, or your plan documents for information on how to direct investments in, or sale from, an investment option corresponding to the Portfolio and any fees that may apply. Participating insurance companies and certain other designated organizations are authorized to receive purchase orders on the Portfolio’s behalf.

TAX INFORMATION

Distributions made by the Portfolio to a Variable Contract or Qualified Plan, and exchanges and redemptions of Portfolio shares made by a Variable Contract or Qualified Plan, ordinarily do not cause the corresponding contract holder or plan participant to recognize income or gain for federal income tax purposes. See the accompanying contract prospectus or the governing documents of your Qualified Plan for information regarding the federal income tax treatment of the distributions to your Variable Contract or Qualified Plan and the holders of the contracts or plan participants.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

If you invest in the Portfolio through a Variable Contract issued by an insurance company or through a Qualified Plan that, in turn, was purchased or serviced through an insurance company, broker-dealer or other financial intermediary, the Portfolio and its adviser or distributor or their affiliates may: (1) make payments to the insurance company issuer of the Variable Contract or to the company servicing the Qualified Plan; and (2) make payments to the insurance company, broker-dealer or other financial intermediary. These payments may create a conflict of interest by: (1) influencing the insurance company or the company servicing the Qualified Plan to make the Portfolio available as an investment option for the Variable Contract or the Qualified Plan; or (2) by influencing the broker-dealer or other intermediary and your salesperson to recommend the Variable Contract or the pension servicing agent and/or the Portfolio over other options. Ask your salesperson or Qualified Plan administrator or visit your financial intermediary’s website for more information.