Primary Investment Strategies

In pursuit of this goal, the fund normally invests at least 80% of its net assets in equity securities issued by U.S. mid-capitalization value companies. Although a universal definition of mid-capitalization companies does not exist, the fund generally defines these companies as those with market capitalizations comparable in size to the companies in the Russell Midcap ^® Value Index (between approximately $563 million and $18.1 billion as of December 31, 2005). In the future, the fund may define mid-capitalization companies using a different index or classification system. The fund primarily buys common stock but also can invest in preferred stock and securities convertible into common and preferred stock. From time to time the fund may invest in shares of companies through initial public offerings (IPOs).

The fund manager is seeking mid-capitalization stocks which he believes are worth more than is indicated by current market price. The manager initially screens for “value” stocks from the universe of U.S. mid-capitalization companies. The manager uses fundamental analysis to examine each company for financial strength before deciding to purchase the stock.

The fund generally will sell a stock when it reaches a target price, which is when the manager believes it is fully valued or when, in the manager’s opinion, conditions change such that the risk of continuing to hold the stock is unacceptable when compared to its growth potential.

It is possible that in extreme market conditions the fund temporarily may invest some or all of its assets in high quality money market securities. Such a temporary defensive strategy would be inconsistent with the fund’s primary investment strategies. The reason for acquiring money market securities would be to avoid market losses. However, if market conditions improve, this strategy could result in reducing the potential gain from the market upswing, thus reducing the fund’s opportunity to achieve its investment goal.

As part of its normal operations, the fund may hold high quality money market securities pending investments or when it expects to need cash to pay redeeming shareholders. The fund will not deviate from its normal strategies if it holds these securities pending investments.

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The fund manager may, when consistent with the fund’s investment goal, buy or sell options or futures on a security or an index of securities (commonly known as derivatives). An option is the right to buy or sell a security or an index of securities at a specific price on or before a specific date. A future is an agreement to buy or sell a security or an index of securities at a specified price on a specified date. The primary purpose of using derivatives is to attempt to reduce risk to the fund as a whole (hedge) but they may also be used to maintain liquidity and commit cash pending investment. The fund manager also may, but under normal market conditions generally does not intend to, use derivatives for speculation to increase returns.

The fund may engage in active and frequent trading of portfolio securities to achieve its primary investment strategies.

Should the Fund’s Board of Trustees determine that the investment goal of the fund should be changed, shareholders will be given at least 30 days notice before any such change is made. However, such change can be effected without shareholder approval.

Key Risks

The main risk of any investment in stocks is that values fluctuate in price. The value of your investment can go up or down depending upon market conditions, which means you could lose money.

Because different kinds of stocks go in and out of favor depending on market conditions, this fund’s performance may be better or worse than other funds with different investment styles. For example, in some markets a fund holding mid-cap growth stocks may outperform this fund.

There is more business risk in investing in mid-capitalization companies than in larger, better capitalized companies. These organizations will normally have more limited product lines, markets and financial resources and will be dependent upon a more limited management group than larger capitalized companies.

IPOs and companies that have recently gone public have the potential to produce substantial gains for the fund. However, there is no assurance that the fund will have access to profitable IPOs and therefore investors should not rely on these past gains as an indication of future performances. The investment performance of the fund during periods when it is unable to invest significantly or at all in IPOs may be lower than during periods when the fund is able to do so. In addition, as the fund increases in size, the impact of IPOs on the fund’s performance will generally decrease. Securities issued in IPOs are subject to many of the same risks as investing in companies with smaller market capitalizations. Securities issued in IPOs have no trading history, and information about the companies may be available for very limited periods. In

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addition, the prices of securities sold in IPOs may be highly volatile or may decline shortly after the initial public offering.

While the fund manager chooses stocks he believes to be undervalued, there is no guarantee that the investments will increase in value or that they won’t decline.

The fund may invest in securities prior to their date of issue. These securities could fall in value by the time they are actually issued, which may be any time from a few days to over a year.

The fund’s use of derivatives may reduce the fund’s returns and/or increase volatility. Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the fund’s use of derivatives is that the fluctuations in their values may not correlate perfectly with the overall securities markets. Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. In addition, some derivatives are more sensitive to interest rate changes and market price fluctuations than other securities. The possible lack of a liquid secondary market for derivatives and the resulting inability of the fund to sell or otherwise close a derivatives position could expose the fund to losses. The fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Finally, BlackRock may not be able to predict correctly the direction of securities prices, interest rates and other economic factors, which could cause the fund’s derivatives positions to lose value.

High portfolio turnover (more than 100%) may result in increased transaction costs to the fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of fund securities may result in the recognition of capital gain or loss. Given the frequency of sales, such gain or loss will likely be short-term capital gain or loss. These effects of higher than normal portfolio turnover may adversely affect fund performance.

When you invest in this fund you are not making a bank deposit. Your investment is not insured or guaranteed by the Federal Deposit Insurance Corporation or by any bank or governmental agency.

Risk / Return Information

On January 31, 2005, the fund reorganized with the State Street Research Mid-Cap Value Fund (the SSR Fund). The SSR Fund transferred substantially all of its assets and liabilities to the fund in exchange for shares of the fund, which were then distributed to SSR Fund shareholders. For periods prior to January 31, 2005, the chart and table below show performance information for the SSR Fund, which had similar investment goals and strategies as the fund. Since R Shares of the fund have no performance history, the chart and table give you a picture of long-term performance

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for Investor A Shares. Although the chart and table show returns for the Investor A Shares which are not offered in this Prospectus, the Investor A Shares would have substantially similar annual returns as the R Shares offered in this Prospectus because the Investor A Shares and the R Shares are invested in the same portfolio of securities and the annual returns would differ only to the extent that the Investor A Shares and the R Shares do not have the same expenses. The actual return of R Shares would have been lower than that of Investor A Shares because R Shares have higher expenses than Investor A Shares. Investor A Shares of the fund are estimated to have expenses of 1.25% of average daily net assets (after waivers and reimbursements) for the current fiscal year and R Shares of the fund are expected to have expenses of 1.68% of average daily net assets (after waivers and reimbursements) for the current fiscal year. The information shows you how performance has varied year by year and provides some indication of the risks of investing in the fund. The table compares the performance to that of the Russell Midcap ^® Value Index, a recognized unmanaged index of stock market performance. As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges are not reflected in the bar chart. If they were, returns would be less than those shown. If certain expenses had not been waived or reimbursed during these periods, returns would have been lower.

The performance of the Investor A Shares of the fund prior to January 31, 2005 is based on the performance of the A Shares of the SSR Fund.

ANNUAL TOTAL RETURNS*

The fund's year to date total return as of 6/30/06 was 4.79%.

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IMPORTANT DEFINITIONS

Advisory Fees: Fees paid to the investment adviser for portfolio management services.

Distribution Fees: Fees paid to the fund’s distributor, BlackRock and service organizations for distribution of fund shares and related sales support services.

Other Expenses: Include administration, transfer agency, custody, professional fees and registration fees.

Service Fees: Fees that are paid to service organizations that provide services to shareholders.

Service Organizations: Brokers, dealers, financial institutions and industry professionals that provide support services to their customers who own shares of the Fund.

As of 12/31/05

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

Expenses and Fees

The table below explains your pricing options and describes the fees and expenses that you may pay if you buy and hold R Shares of the fund.

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. We are assuming an initial investment of $10,000, 5% total return each year with no changes in operating expenses and redemption at the end of each time period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

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As a shareholder you pay certain fees and expenses. Shareholder transaction fees are paid out of your investment and annual fund operating expenses are paid out of fund assets.