MFS Blended Research Small Cap Equity Fund

MFS Blended Research Small Cap Equity Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy and hold shares of the fund, which are not reflected below. Expenses for Class 529B shares have been adjusted to reflect the full impact of the distribution fee.

You may qualify for sales charge reductions if, with respect to Class A or Class 529A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 11 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees - MFS Blended Research Small Cap Equity Fund	A		B	C	I	R1	R2	R3	R4	R6	529A	529B	529C
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	none	none	none	none	none	5.75%	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%	1.00%	none	none	none	none	none	none	none	4.00%	1.00%

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

Annual Fund Operating Expenses - MFS Blended Research Small Cap Equity Fund		A	B	C	I	R1	R2	R3	R4	R6	529A	529B	529C
Management Fee		0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none	0.25%	1.00%	1.00%
Other Expenses		0.26%	0.26%	0.26%	0.26%	0.26%	0.26%	0.26%	0.26%	0.17%	0.31%	0.31%	0.31%
Total Annual Fund Operating Expenses		1.16%	1.91%	1.91%	0.91%	1.91%	1.41%	1.16%	0.91%	0.82%	1.21%	1.96%	1.96%
Fee Reductions and/or Expense Reimbursements	[1]	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.12%)	(0.17%)	(0.17%)	(0.17%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.99%	1.74%	1.74%	0.74%	1.74%	1.24%	0.99%	0.74%	0.70%	1.04%	1.79%	1.79%

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 you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example - MFS Blended Research Small Cap Equity Fund - USD ($)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	670	906	1,161	1,889
B	577	884	1,216	2,024
C	277	584	1,016	2,219
I	76	273	487	1,104
529A	675	921	1,186	1,942
529B	582	899	1,242	2,077
529C	282	599	1,042	2,272
R1	177	584	1,016	2,219
R2	126	430	755	1,676
R3	101	352	622	1,394
R4	76	273	487	1,104
R6	72	250	443	1,002

Expense Example No Redemption - MFS Blended Research Small Cap Equity Fund - USD ($)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	177	584	1,016	2,024
C	177	584	1,016	2,219
529B	182	599	1,042	2,077
529C	182	599	1,042	2,272

Portfolio Turnover

The fund 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 transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction 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 fund’s portfolio turnover rate was 75% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) seeks to achieve the fund’s objective by actively identifying potential investments based on fundamental and quantitative analysis and then constructing a portfolio from these potential investments while managing various risk factors (e.g., issuer, industry, and sector weightings, market capitalization, and volatility) compared to the Russell 2000® Index, which represents the fund’s investment universe.

MFS normally invests at least 80% of the fund’s net assets in equity securities of issuers with small market capitalizations. MFS generally defines small market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell 2000® Index over the last 13 months at the time of purchase. As of August 31, 2020, the range of the market capitalizations of the issuers in the Russell 2000® Index was between approximately $50.29 million and $7.37 billion.

Equity securities include common stocks, equity interests in real estate investment trusts (REITs), and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer.

In selecting investments for the fund, MFS is not constrained by any particular investment style. MFS may invest the fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (growth companies), in the stocks of companies it believes are undervalued compared to their perceived worth (value companies), or in a combination of growth and value companies.

MFS may invest the fund’s assets in foreign securities.

MFS normally invests the fund’s assets across different industries and sectors, but MFS may invest a significant percentage of the fund’s assets in issuers in a single industry or sector.

MFS uses an active bottom-up approach to buying and selling investments for the fund. Investments are selected primarily based on blending fundamental and quantitative research. MFS uses fundamental analysis of individual issuers to determine a fundamental rating for an issuer.  MFS uses quantitative analysis to determine a quantitative rating for an issuer. MFS combines the fundamental rating with the quantitative rating to create a blended rating for an issuer. When an MFS fundamental rating is not available, MFS treats the issuer as having a neutral fundamental rating.

MFS constructs the portfolio using a portfolio optimization process that considers the blended rating, as well as issuer, industry, and sector weightings, market capitalization, volatility, and other factors.  The portfolio managers have the discretion to adjust the inputs and parameters used in the optimization process and the fund’s portfolio holdings based on factors such as the desired portfolio characteristics and the portfolio managers’ qualitative assessment of the optimization results.  MFS’ goal is to construct an actively managed portfolio with a target predicted tracking error of approximately 3% compared to the Russell 2000® Index.  Tracking error generally measures how the differences between the fund’s returns and the Russell 2000® Index’s returns have varied over a period of time.

For purposes of the fund’s 80% policy, net assets include the amount of any borrowings for investment purposes.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Investment Selection Risk:  MFS’ investment analysis, its development and use of quantitative models, and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. The quantitative models used by MFS (both proprietary and third-party) may not produce the intended results for a variety of reasons, including the factors used in the models, the weight placed on each factor in the models, changes from the market factors’ historical trends, changing sources of market return or market risk, and technical issues in the design, development, implementation, application, and maintenance of the models (e.g., incomplete, stale, or inaccurate data, programming or other software issues, coding errors, and technology failures).

Equity Market Risk/Company Risk:  Equity markets are volatile and can decline significantly in response to, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.  These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general.  Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market.

Investment Strategy Risk:  There is no assurance that the fund’s predicted tracking error will equal its target predicted tracking error at any point in time or consistently for any period of time, or that the fund’s predicted tracking error and actual tracking error will be similar.  The fund’s strategy to target a predicted tracking error of approximately 3% compared to the Russell 2000® Index and to blend fundamental and quantitative research may not produce the intended results. In addition, MFS fundamental research is not available for all issuers.

Small Cap Risk:  The stocks of small cap companies can be more volatile and their shares can be less liquid than those of larger companies.

Foreign Risk:  Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to emerging and frontier markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

REITs Risk: The risks of investing in REITs include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; difficulties in valuing and disposing of real estate; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; the management skill and creditworthiness of the REIT manager; and other factors.  The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

Focus Risk:  Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund’s performance will be affected by the conditions in the industries, sectors, countries and regions to which the fund is exposed.

Liquidity Risk:  It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares.  These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices.  Redemptions of a large number of shares also may increase transaction costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart. 

The total return for the six-month period ended June 30, 2020, was (19.11)%. During the period(s) shown in the bar chart, the highest quarterly return was 16.72% (for the calendar quarter ended March 31, 2019) and the lowest quarterly return was (18.57)% (for the calendar quarter ended December 31, 2018).

Performance Table.

Average Annual Total Returns (For the Periods Ended December 31, 2019)

Average Annual Returns - MFS Blended Research Small Cap Equity Fund	Average Annual Returns, 1 Year	Average Annual Returns, Since Inception	Average Annual Returns, Inception Date
B	21.02%	10.33%	Sep. 15, 2015
C	23.95%	10.68%	Sep. 15, 2015
I	26.23%	11.79%	Sep. 15, 2015
529A	18.63%	9.93%	Sep. 15, 2015
529B	20.96%	10.29%	Sep. 15, 2015
529C	23.89%	10.62%	Sep. 15, 2015
R1	25.06%	10.67%	Sep. 15, 2015
R2	25.63%	11.21%	Sep. 15, 2015
R3	25.94%	11.50%	Sep. 15, 2015
R4	26.28%	11.78%	Sep. 15, 2015
R6	26.28%	11.85%	Sep. 15, 2015
A	18.68%	9.98%	Sep. 15, 2015
After Taxes on Distributions | A	18.14%	8.98%
After Taxes on Distributions and Sale of Fund Shares | A	11.27%	7.46%
Russell 2000® Index	25.52%	10.52%	Sep. 15, 2015

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. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns

are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.

[1] Massachusetts Financial Services Company has agreed in writing to bear the fund’s expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund’s investment activity), such that “Total Annual Fund Operating Expenses” do not exceed 0.99% of the class’ average daily net assets annually for each of Class A and Class R3 shares, 1.74% of the class’ average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.74% of the class’ average daily net assets annually for each of Class I and Class R4 shares, 1.24% of the class’ average daily net assets annually for Class R2 shares, 0.70% of the class’ average daily net assets annually for Class R6 shares, 1.04% of the class’ average daily net assets annually for Class 529A shares, and 1.79% of the class’ average daily net asset annually for each of Class 529B and Class 529C shares. This written agreement will continue until modified by the fund’s Board of Trustees, but such agreement will continue until at least September 30, 2021.