Transamerica U.S. Equity Index VP

Transamerica U.S. Equity Index VP

Investment Objective:

Seeks to provide investment results that, before expenses, correspond generally to the price and yield performance of the S&P 500® Index.

Fees and Expenses:

This table describes the fees and expenses that you may pay if you buy and hold portfolio shares, but it does not reflect any charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, fees would be higher.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees	Transamerica U.S. Equity Index VP Service
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	none
Maximum deferred sales charge (load) (as a percentage of purchase price or redemption proceeds, whichever is lower)	none

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

Annual Fund Operating Expenses - Transamerica U.S. Equity Index VP		Initial	Service
Management fees		0.08%	0.08%
Distribution and service (12b-1) fees		none	0.25%
Other expenses		0.70%	0.70%
Total annual fund operating expenses		0.78%	1.03%
Fee waiver and/or expense reimbursement	[1]	0.64%	0.64%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.14%	0.39%

Example:

This Example is intended to help you compare the cost of investing in the portfolio with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the portfolio for the time periods indicated and then redeem all shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the portfolio’s operating expenses remain the same. The Example does not reflect charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, costs would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - Transamerica U.S. Equity Index VP - USD ($)	1 year	3 years	5 years	10 years
Initial Class	14	185	370	906
Service Class	40	264	506	1,201

Portfolio Turnover:

During the period beginning May 1, 2017 through December 31, 2017, the portfolio turnover rate for the portfolio was 4.21% of the average value of its portfolio.

Principal Investment Strategies:

Under normal circumstances, the portfolio invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities listed in the S&P 500® Index (the “Index”)1. Under normal circumstances, however, the portfolio intends to invest substantially all of its assets in securities of companies included in the Index and close substitutes, including index futures contracts. The Index is a well-known stock market index that includes common stocks of approximately 500 companies from all major industries representing a significant portion of the market value of all common stocks publicly traded in the United States. Stocks in the Index are weighted according to their float adjusted capitalizations. The Index, which is constructed and maintained by S&P Dow Jones Indices LLC, is rebalanced each March, June, September and December, and is reconstituted on an as needed basis and on pre-determined dates as constituents change in size. The portfolio will concentrate (invest 25% or more of the value of its assets) in the securities of issuers having their principal business activities in the same industry if the Index is also concentrated in such industry.

The portfolio’s sub-adviser, SSGA Funds Management, Inc. (the “sub-adviser”), does not sub-advise the portfolio according to traditional methods of “active” investment management, which involve the buying and selling of securities based upon economic, financial and market analysis and investment judgment. Instead, the sub-adviser utilizes a “passive” or “indexing” investment approach, seeking to provide investment results that, before expenses, correspond generally to the total return performance of the Index by employing a sampling strategy.

The sub-adviser seeks to replicate the returns of the Index by investing in the securities of the Index in approximately their Index weight. However, under various circumstances, it may not be possible or practicable to purchase all of those securities in those weightings. In those circumstances, the portfolio may purchase a sample of stocks in the Index in proportions expected to replicate generally the performance of the Index as a whole. In addition, from time to time, stocks are added to or removed from the Index. The portfolio may sell stocks that are represented in the Index, or purchase stocks that are not yet represented in the Index, in anticipation of their removal from or addition to the Index.

The sub-adviser may at times purchase or sell futures contracts in lieu of investment directly in the stocks making up the Index. The sub-adviser might do so, for example, in order to increase the portfolio’s investment exposure pending investment of cash in the stocks comprising the Index. Alternatively, the sub-adviser might use futures to reduce its investment exposure to the Index in situations where it intends to sell a portion of the stocks in the portfolio but the sale has not yet been completed.

1 Standard & Poor’s does not sponsor the portfolio, nor is it affiliated in any way with the portfolio or the portfolio’s advisers. “Standard & Poor’s®,” “S&P®,” “S&P 500®,” and “Standard & Poor’s 500®” are trademarks of McGraw-Hill, Inc. The portfolio is not sponsored, endorsed, sold or promoted by Standard & Poor’s and Standard & Poor’s makes no representation or warranty, express or implied, regarding the advisability of investing in the portfolio.

Principal Risks:

Risk is inherent in all investing. Many factors affect the portfolio's performance. The value of your investment in the portfolio, as well as the amount of return you receive on your investment, may fluctuate significantly. You may lose part or all of your investment in the portfolio or your investment may not perform as well as other similar investments. The following is a summary description of principal risks (in alphabetical order) of investing in the portfolio. An investment in the portfolio is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. You may lose money if you invest in this portfolio.

Counterparty – The portfolio will be subject to credit risk (meaning the risk of adverse changes in an issuer’s real or perceived financial strength) with respect to counterparties to derivatives, repurchase agreements and other financial contracts entered into by the portfolio or held by special purpose or structured vehicles. Adverse changes to counterparties may cause the value of financial contracts to go down. If a counterparty becomes bankrupt or otherwise fails to perform its obligations, the value of your investment in the portfolio may decline.

Derivatives – Using derivatives exposes the portfolio to additional risks and can increase portfolio losses and reduce opportunities for gains when market prices, interest rates, currencies, or the derivatives themselves, behave in a way not anticipated by the portfolio. Using derivatives may have a leveraging effect, increase portfolio volatility and not produce the result intended. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the portfolio. Derivatives are generally subject to the risks applicable to the assets, rates, indices or other indicators underlying the derivative. The value of a derivative may fluctuate more than, or otherwise not correlate well with, the underlying assets, rates, indices or other indicators to which it relates. Use of derivatives may have different tax consequences for the portfolio than an investment in the underlying security, and those differences may affect the amount, timing and character of income distributed to shareholders. The U.S. government and foreign governments are in the process of adopting and implementing regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make derivatives more costly, limit their availability or utility, otherwise adversely affect their performance, or disrupt markets. For additional information regarding derivatives, see “More on Risks of Investing in the Portfolio—More on Principal Risks: Derivatives” in this prospectus. In addition, the SEC has proposed a new rule that would change the regulation of the use of derivatives by registered investment companies, such as the portfolio. If the proposed rule, or a different rule, takes effect, it could limit the ability of the portfolio to invest in derivatives.

Equity Securities – Equity securities represent an ownership interest in an issuer, rank junior in a company’s capital structure and consequently may entail greater risk of loss than debt securities. Equity securities include common and preferred stocks. Stock markets are volatile. Equity securities may have greater price volatility than other asset classes, such as fixed income securities, and fluctuate based on changes in a company’s financial condition and overall market and economic conditions. If the market prices of the equity securities owned by the portfolio fall, the value of your investment in the portfolio will decline. If the portfolio holds equity securities in a company that becomes insolvent, the portfolio’s interests in the company will rank junior in priority to the interests of debtholders and general creditors of the company.

Index Fund – While the portfolio seeks to track the performance of the S&P 500® (i.e., achieve a high degree of correlation with the index), the portfolio’s return may not match the return of the index. The portfolio incurs a number of operating expenses not applicable to the index, and incurs costs in buying and selling securities. In addition, the portfolio may not be fully invested at times, generally as a result of cash flows into or out of the portfolio or reserves of cash held by the portfolio to meet redemptions. The portfolio may attempt to replicate the index return by investing in fewer than all of the securities in the index, or in some securities not included in the index, potentially increasing the risk of divergence between the portfolio’s return and that of the index.

Industry Concentration – The portfolio will concentrate its investments in issuers of one or more particular industries to the same extent that its underlying index is so concentrated and to the extent permitted by applicable regulatory guidance. Concentration in a particular industry subjects the portfolio to the risks associated with that industry. As a result, the portfolio may be subject to greater price volatility and risk of loss as a result of adverse economic, business or other developments affecting that industry than portfolios investing in a broader range of industries.

Large Capitalization Companies – The portfolio’s investments in large capitalization companies may underperform other segments of the market because they may be less responsive to competitive challenges and opportunities and unable to attain high growth rates during periods of economic expansion. As a result, the portfolio’s value may not rise as much as, or may fall more than, the value of portfolios that focus on companies with smaller market capitalizations.

Legal and Regulatory – Legal and regulatory changes could occur that may adversely affect the portfolio, its investments, and its ability to pursue its investment strategies and/or increase the costs of implementing such strategies. New or revised laws or regulations may be imposed by the U.S. Securities and Exchange Commission, the U.S. Commodity Futures Trading Commission, the Internal Revenue Service, the U.S. Federal Reserve or other governmental regulatory authorities or self-regulatory organizations that could adversely affect the portfolio. The portfolio also may be adversely affected by changes in the enforcement or interpretation of existing statutes and rules by governmental regulatory authorities or self-regulatory organizations.

Liquidity – The portfolio may make investments that are illiquid or that become illiquid after purchase. Investments may become illiquid due to the lack of an active market, a reduced number of traditional market participants, or reduced capacity of traditional market participants to make a market in securities. The liquidity and value of investments can deteriorate rapidly and those investments may be difficult or impossible for the portfolio to sell, particularly during times of market turmoil. Illiquid investments can be difficult to value. Markets may become illiquid when, for instance, there are few, if any, interested buyers or sellers or when dealers are unwilling to make a market for certain securities. As a general matter, dealers recently have been less willing to make markets for fixed income securities. If the portfolio is forced to sell an illiquid investment to meet redemption requests or other cash needs, the portfolio may be forced to sell at a loss. The portfolio may not receive its proceeds from the sale of securities for an extended period (for example, several weeks or even longer).

Management – The portfolio is subject to the risk that the investment manager’s or sub-adviser’s judgments and decisions may be incorrect or otherwise may not produce the desired results. The value of your investment may decrease if the investment manager’s or sub-adviser’s judgment about the quality, relative yield or value of, or market trends affecting, a particular security or issuer, industry, sector, region or market segment, or about the economy or interest rates, is incorrect. The portfolio may also suffer losses if there are imperfections, errors or limitations in the quantitative, analytic or other tools, resources, information and data used, or the analyses employed or relied on, by the investment manager or sub-adviser, or if the investment manager’s or sub-adviser’s investment style is out of favor or otherwise fails to produce the desired results. The portfolio’s investment strategies designed by the investment manager or sub-adviser may not work as intended. In addition, the portfolio’s investment strategies or policies may change from time to time. Those changes may not lead to the results intended by the investment manager or sub-adviser and could have an adverse effect on the value or performance of the portfolio. Any of these things could cause the portfolio to lose value or its results to lag relevant benchmarks or other funds with similar objectives.

Market – The value of the portfolio's securities may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates or currency rates, lack of liquidity in the markets or adverse investor sentiment. Adverse market conditions may be prolonged and may not have the same impact on all types of securities. The value of securities also may go down due to events or conditions that affect particular sectors, industries or issuers. If the value of the securities owned by the portfolio fall, the value of your investment will go down. The portfolio may experience a substantial or complete loss on any individual security.

In the past decade, financial markets throughout the world have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. Governmental and non-governmental issuers have defaulted on, or been forced to restructure, their debts. These market conditions may continue, worsen or spread. Events that have contributed to these market conditions include, but are not limited to, major cybersecurity events; geopolitical events (including wars and terror attacks); measures to address budget deficits; downgrading of sovereign debt; declines in oil and commodity prices; dramatic changes in currency exchange rates; and public sentiment. The European Union has experienced increasing stress for a variety of reasons, including economic downturns in various member countries. In June 2016, the United Kingdom voted to withdraw from the European Union, and additional members could do the same. The impact of these conditions and events is not yet known.

The U.S. government and the Federal Reserve, as well as certain foreign governments and central banks have taken steps to support financial markets, including by keeping interest rates at historically low levels. This and other government interventions may not work as intended, particularly if the efforts are perceived by investors as being unlikely to achieve the desired results. The Federal Reserve has reduced its market support activities and has begun raising interest rates. Certain foreign governments and central banks are implementing or discussing so-called negative interest rates (e.g., charging depositors who keep their cash at a bank) to spur economic growth. Further Federal Reserve or other U.S. or non-U.S. governmental or central bank actions, including interest rate increases or contrary actions by different governments could negatively affect financial markets generally, increase market volatility, and reduce the value and liquidity of securities in which the portfolio invests.

Policy and legislative changes in the United States and in other countries are affecting many aspects of financial regulation, and may in some instances contribute to decreased liquidity and increased volatility in the financial markets. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time.

Economies and financial markets throughout the world are increasingly interconnected. Economic, financial or political events, trading and tariff arrangements, terrorism, natural disasters and other circumstances in one country or region could have profound impacts on global economies or markets. As a result, whether or not the portfolio invests in securities of issuers located in or with significant exposure to the countries directly affected, the value and liquidity of the portfolio's investments may be negatively affected.

New Portfolio – The portfolio is newly formed. Investors in the portfolio bear the risk that the sub-adviser may not be successful in implementing its investment strategy, and may not employ a successful investment strategy, or that the portfolio may fail to attract sufficient assets under management to realize economies of scale, any of which could result in the portfolio being liquidated at any time without shareholder approval and at a time that may not be favorable for all shareholders. Further, a portfolio initially seeded with assets below a certain threshold may realize significant tracking error relative to the portfolio’s underlying index due to the initial seeding amount and such tracking error will be reflected in the portfolio’s performance.

Passive Strategy/Index – The portfolio is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities, regardless of the current or projected performance of the Index or of the actual securities comprising the Index. This differs from an actively-managed fund, which typically seeks to outperform a benchmark index. As a result, the portfolio’s performance may be less favorable than that of a portfolio managed using an active investment strategy. The structure and composition of the Index will affect the performance, volatility, and risk of the Index and, consequently, the performance, volatility, and risk of the portfolio.

Performance:

No performance is shown for the portfolio. Performance information will appear in a future version of this prospectus once the portfolio has a full calendar year of performance information to report to investors. The portfolio's primary benchmark is the S&P 500®.

As with all mutual funds, past performance (before and after taxes) is not a prediction of future results. Updated performance information is available on our website at www.transamericaseriestrust.com/content/Performance.aspx or by calling 1-888-233-4339.

[1] Contractual arrangements have been made with the portfolio’s investment manager, Transamerica Asset Management, Inc. (“TAM”), through May 1, 2019 to waive fees and/or reimburse portfolio expenses to the extent that the total annual fund operating expenses exceed 0.14% for Initial Class shares and 0.39% for Service Class shares, excluding, as applicable, acquired fund fees and expenses, interest, taxes, brokerage commissions, dividend and interest expenses on securities sold short, extraordinary expenses and other expenses not incurred in the ordinary course of the portfolio’s business. These arrangements cannot be terminated prior to May 1, 2019 without the Board of Trustees’ consent. TAM is permitted to recapture amounts waived and/or reimbursed to a class during any of the previous 36 months if the class’ total annual fund operating expenses have fallen to a level below the limits described above. In no case will TAM recapture any amount that would result, on any particular business day of the portfolio, in the class’ total annual fund operating expenses exceeding the applicable limits described above or any other lower limit then in effect.