Mutual Fund Summary Prospectus (497k)

Summary Prospectus April 30, 2013, as supplemented July 1, 2013

ING U.S. Stock Index Portfolio

Class / Ticker

S2 /ISIPX

Before you invest, you may want to review the Portfolio’s Prospectus, which contains more information about the Portfolio and its risks. For free paper or electronic copies of the Prospectus and other Portfolio information (including the Statement of Additional Information and most recent financial report to shareholders), go to www.INGFunds.com/vp/literature; email a request to [e-mail]; call 1-800-366-0066; or ask your salesperson, financial intermediary, or retirement plan administrator. The Portfolio’s Prospectus and Statement of Additional Information, each dated April 30, 2013, as supplemented, and the audited financial statements on pages 30-77 of the Portfolio’s shareholder report dated December 31, 2012 are incorporated into this Summary Prospectus by reference and may be obtained free of charge at the website, phone number, or e-mail address noted above.

INVESTMENT OBJECTIVE

The Portfolio seeks 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 Management Agreement provides for a “bundled fee” arrangement under which the Adviser provides (in addition to advisory services), custodial, administrative, transfer agency, portfolio accounting, auditing and ordinary legal services in return for a single management fee.

Annual Portfolio Operating Expenses Expenses you pay each year as a % of the value of your investment

Class	S2
Management Fee	0.26%
Distribution and/or Shareholder Services (12b-1) Fees	0.50%
Other Expenses	0.01%
Total Annual Portfolio Operating Expenses	0.77%
Waivers and Reimbursements 1	(0.10)%
Total Annual Portfolio Operating Expenses After Waivers and Reimbursements	0.67%

1	The distributor is contractually obligated to waive 0.10% of the distribution fee through May 1, 2014. There is no guarantee that the distribution fee waiver will continue after May 1, 2014. The distribution fee waiver will only renew if the distributor elects to renew it.

Expense Example $

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:

Class			1 Yr	3 Yrs	5 Yrs	10 Yrs
S2		$	68	236	418	945

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.

Portfolio Turnover % of average value of portfolio

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 7% 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 equity securities of companies included in the S&P 500 ^® Index (“Index”) or equity securities of companies that are representative of the Index (including derivatives). The Portfolio will provide shareholders with at least 60 days’ prior notice of any change in this investment policy.

The Portfolio invests principally in common stock and employs a “passive management” approach designed to track the performance of the Index, which is denominated by stocks of large U.S. companies. The Portfolio usually attempts to replicate the target index by investing all, or substantially all, of its assets in stocks that make up the Index. The replication method implies that the Portfolio holds each security found in its target index in approximately the same proportion as represented in the index itself.

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Under certain circumstances, the Portfolio may not hold all of the same securities as the Index. The Portfolio may also invest in stock index futures and other derivatives as a substitute for the sale or purchase of securities in the Index and to provide equity exposure to the Portfolio’s cash position.

In the event that the Portfolio’s market value is $50 million or less, in order to replicate investment in stocks listed on the Index, the sub-adviser (“Sub-Adviser”) may invest the entire amount of the Portfolio’s assets in the index futures, in exchange-traded funds (“ETFs”), or in a combination of the index futures and ETFs, subject to any limitation on the Portfolio’s investments in such securities. ETFs are passively managed investment companies traded on a securities exchange whose goal is to track or replicate a desired index.

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 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 33 ¹ / 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.

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.

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.

Index Strategy   The index selected may underperform the overall market and the Portfolio might fail to track its target index. The correlation between the Portfolio and index performance may be affected by the Portfolio’s expenses and the timing of purchases and redemptions of the Portfolio’s shares. The Portfolio’s actual holdings might not match the Index and the Portfolio’s effective exposure to index securities at any given time may not equal 100%.

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.

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.

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.

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 higher than Class S2 shares’ performance because of the higher expenses paid by Class S2 shares. The Portfolio’s performance

Summary Prospectus

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ING U.S. Stock Index Portfolio

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information reflects applicable fee waivers and/or expense limitations in effect during the period presented. Absent such fee waivers/expense limitations, if any, performance would have been lower. Performance in the Average Annual Total Returns table does not include insurance-related charges imposed under a Variable Contract or expenses related to a Qualified Plan. If these charges or expenses were included, performance would be lower. Thus, you should not compare the Portfolio’s performance directly with the performance information of other investment products without taking into account all insurance-related charges and expenses payable under your Variable Contract or Qualified Plan. The Portfolio’s past performance is no guarantee of future results.

The bar chart below shows the Portfolio’s adjusted Class I shares’ performance (2005-2007) and Class S2 shares’ performance (2008-2012).

Calendar Year Total Returns (as of December 31 of each year)

   

Best quarter: 2nd, 2009, 15.74% and Worst quarter: 4th, 2008, (22.03)%

Average Annual Total Returns% (for the periods ended December 31, 2012)

		1 Yr	5 Yrs	10 Yrs (or since inception)	Inception Date
Class S2	%	15.29	1.01	1.08	08/01/07
S&P 500 ® Index 1	%	16.00	1.66	1.87 2	—
Class I (adjusted)	%	15.32	1.02	4.45	05/03/04
S&P 500 ® Index 1	%	16.00	1.66	5.12 2	—

1	The index returns do not reflect deductions for fees, expenses, or taxes.
2	Reflects index performance since the date closest to the Class’ inception for which data is available.

PORTFOLIO MANAGEMENT

Investment Adviser	Sub-Adviser
Directed Services LLC	ING Investment Management Co. LLC

Portfolio Managers
Steve Wetter	Kai Yee Wong
Portfolio Manager (since 04/12)	Portfolio Manager (since 06/13)

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.

SPRO-IITUSSIS2 (0713-070113)

Summary Prospectus

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ING U.S. Stock Index Portfolio

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SPRO-IITUSSIS2 (0713-070113)

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