0000787441 2012-12-14 2012-12-14 0000787441 ck0000787441:S000006903Member ck0000787441:C000060799Member 2012-12-14 2012-12-14 0000787441 ck0000787441:S000006903Member ck0000787441:C000057100Member 2012-12-14 2012-12-14 0000787441 ck0000787441:S000006903Member ck0000787441:C000018722Member 2012-12-14 2012-12-14 0000787441 ck0000787441:S000006903Member ck0000787441:C000018721Member 2012-12-14 2012-12-14 0000787441 ck0000787441:S000006903Member ck0000787441:C000018720Member 2012-12-14 2012-12-14 0000787441 ck0000787441:S000006903Member ck0000787441:C000018719Member 2012-12-14 2012-12-14 0000787441 ck0000787441:P0001-S000006903Member ck0000787441:S000006903Member 2012-12-14 2012-12-14 Other 2012-12-14 MAINSTAY FUNDS 0000787441 false 2012-12-14 2012-12-14 2012-02-28 MainStay Common Stock Fund   <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">  <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">THE MAINSTAY GROUP OF FUNDS <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">  <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">MainStay Common Stock Fund <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">  <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">Supplement dated December 14, 2012 (“Supplement”) to the Summary Prospectus, Prospectus <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">and Statement of Additional Information, each dated February 28, 2012, as supplemented <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">  <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">This Supplement updates certain information contained in the Summary Prospectus, Prospectus and Statement of Additional Information for MainStay Common Stock Fund (the “Fund”), a series of The MainStay Funds (the “Trust”). You may obtain copies of the Fund’s Summary Prospectus, Prospectus and Statement of Additional Information free of charge, upon request, by calling toll-free 800-MAINSTAY (624-6782), or by writing to NYLIFE Distributors LLC, Attn: MainStay Marketing Department, 169 Lackawanna Avenue, Parsippany, New Jersey 07054. These documents are also available on the Fund’s website at mainstayinvestments.com. Please review this important information carefully. <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">  <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">At a meeting held on December 10-12, 2012, the Trust’s Board of Trustees, including the Independent Trustees, approved the following changes, effective February 28, 2013:   <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">Investment Process Changes <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">  <p class="MsoNormal" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;line-height:normal;text-autospace:none">The Investment Process section of the Summary Prospectus and Prospectus is changed to read as follows: <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.5in;margin-bottom:0in; margin-left:.5in;margin-bottom:.0001pt;text-align:justify;line-height:normal; text-autospace:none">  <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.5in;margin-bottom:0in; margin-left:40.5pt;margin-bottom:.0001pt;text-align:justify;line-height:normal; text-autospace:none">Investment Process: Madison Square Investors LLC, the Fund's Subadvisor, seeks to construct a broadly-diversified portfolio across sectors and industries using quantitative analysis to identify undervalued and overvalued securities. Investments are selected using an objective, disciplined and broadly-applied process while limiting exposure to risk. The Subadvisor seeks to control the Fund's exposure to risk by diversifying the Fund's portfolio over a large number of securities. <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.5in;margin-bottom:0in; margin-left:40.5pt;margin-bottom:.0001pt;text-align:justify;line-height:normal; text-autospace:none">  <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.5in;margin-bottom:0in; margin-left:40.5pt;margin-bottom:.0001pt;text-align:justify;line-height:normal; text-autospace:none">In unusual market conditions, the Fund may invest all or a portion of its assets in investment grade notes and bonds, cash and cash equivalents. <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.5in;margin-bottom:0in; margin-left:40.5pt;margin-bottom:.0001pt;text-align:justify;line-height:normal; text-autospace:none">  <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.5in;margin-bottom:0in; margin-left:40.5pt;margin-bottom:.0001pt;text-align:justify;line-height:normal; text-autospace:none">The Subadvisor may sell a security if it no longer believes the security will contribute to meeting the investment objective of the Fund, if better opportunities are identified, or if it determines the initial investment expectations are not being met. <p class="MsoNormal" style="font-size:11.0pt;font-family:'calibri','sans-serif';margin-top:0in;margin-right:.5in;margin-bottom:0in; margin-left:40.5pt;margin-bottom:.0001pt;text-align:justify;line-height:normal; text-autospace:none">    <p class="MsoNormal" align="center" style="margin-top:0in;margin-right:0in;margin-left:0in;font-size:11.0pt;font-family:'calibri','sans-serif';margin-bottom:0in;margin-bottom:.0001pt; text-align:center;line-height:normal;text-autospace:none">PLEASE RETAIN THIS SUPPLEMENT FOR YOUR FUTURE REFERENCE.   MSOAX MOPBX MGOCX MSOIX MSORX MCSSX