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<P align=center><FONT size=5><B>SECURITIES AND EXCHANGE COMMISSION<BR></B></FONT><FONT size=2><B>Washington, D.C. 20549 </B></FONT></P><HR align=center width=120 noShade><P align=center><FONT size=5><B>FORM 8-K<BR></B></FONT><FONT size=2><B>CURRENT REPORT </B></FONT></P><P align=center><FONT size=2><B>
Pursuant to Section&nbsp;13 or 15(d) of the<BR>Securities Exchange Act of 1934 </B></FONT></P><P align=center><FONT size=2>Date of Report (date of earliest event reported):&nbsp; May 25, 2005<BR>&nbsp;</FONT></P><HR align=center width=120 noShade><P align=center><FONT size=5><B>WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.</B></FONT>
<P align=center>
<FONT size=3><B>WASHINGTON MUTUAL MSC MORTGAGE PASS-THROUGH CERTIFICATES<BR>
SERIES 2005-RA1</B></FONT>
<FONT size=2><BR>(Exact name of Registrant as specified in its charter) </FONT></P>
<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0>
<TR vAlign=top>
<TD align=middle width="32%"><FONT size=2><B>Delaware</B></FONT></TD>
<TD align=middle width="32%"><FONT size=2><B>333-103345-64</B></FONT></TD>
<TD align=middle width="32%"><FONT size=2><B>94-2528990</B></FONT></TD>
<TR vAlign=top>
<TD align=middle width="32%"><FONT size=2>
(State or other jurisdiction<BR>of incorporation)</FONT></TD><TD align=middle width="32%"><FONT size=2>
(Commission File Number)</FONT></TD><TD align=middle width="32%"><FONT size=2>(I.R.S. Employer<BR>Identification No.)</FONT></TD></TR></TABLE>
<P align=center><FONT size=2><B>
1201 THIRD AVENUE, WMT 1706<BR>
SEATTLE, WASHINGTON 98101<BR></FONT></B>
<FONT size=2>(Address of principal executive offices and Zip Code) </FONT></P>
<P align=center><FONT size=2>Registrant's telephone number, including area code:
(206)&nbsp;377-8555
</FONT></P>
<HR noShade><P>&nbsp;</P>
<P><FONT face="Times New Roman" size=2>SECTION 8.&nbsp; OTHER EVENTS</FONT></P>
<P><FONT face="Times New Roman" size=2>ITEM 8.01  Other Events<BR></P>&nbsp;&nbsp;&nbsp;&nbsp;
This Current Report on Form 8-K relates to the distribution report furnished to certificate holders in connection with the May 2005 distribution.</FONT></P><P><FONT face="Times New Roman" size=2>
SECTION 9.&nbsp;&nbsp;&nbsp; FINANCIAL STATEMENTS AND EXHIBITS</FONT></P>
<P><FONT face="Times New Roman" size=2>ITEM 9.01 Financial Statements and Exhibits</FONT></P>
<P><FONT face="Times New Roman" size=2>(a) Not applicable</FONT></P>
<P><FONT face="Times New Roman" size=2>(b) Not applicable</FONT></P>
<P><FONT face="Times New Roman" size=2>(c)&nbsp; Exhibits</FONT></P>
<TABLE style="BORDER-COLLAPSE: collapse" borderColor=#111111 height=82 cellSpacing=0 cellPadding=0 width=543 border=0><TR><TD vAlign=bottom width=163 height=18><P align=center><FONT face="Times New Roman" size=2>Exhibit No.</FONT></P></TD><TD vAlign=bottom width=748 height=18><P align=center><FONT face="Times New Roman"size=2>Description</FONT></P></TD></TR><TR><TD vAlign=top width=163 height=19><HR width="90%" color=#000000 SIZE=1></TD>
<TD vAlign=top width=748 height=19><HR width="90%" color=#000000 SIZE=1></TD></TR>
<TR><TD vAlign=top width=163 height=45><P align=center><FONT face="Times New Roman" size=2>99.1</FONT></P></TD>
<TD vAlign=top width=748 height=45>
<P align=center><FONT face="Times New Roman" size=2>
Washington Mutual MSC<br>Mortgage Pass-Through Certificates, Series 2005-RA1<BR>
Monthly Distribution Report for May 2005
</FONT></P></TD></TR></TABLE>
<P>&nbsp;</P><P>&nbsp;</P><P align=center><FONT size=2>2</FONT></P><HR noShade>
<P align=center><FONT size=2><B>SIGNATURES </B></FONT></P>
<P><FONT size=2>&nbsp;&nbsp;&nbsp;&nbsp;
Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
</FONT></P><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0>
<TR align=middle>
<TD width="47%"><FONT size=2>&nbsp;</FONT></TD>
<TD width="2%"><FONT size=2>&nbsp;</FONT></TD><TD width="51%" colSpan=3><FONT size=2>
WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.<br></FONT></TD></TR>
<TR vAlign=top><TD width="47%"><FONT size=2><BR>
Date:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; May 27, 2005<TD width="2%"><FONT size=2><BR>&nbsp;</FONT></TD>
<TD width="5%"><FONT size=2><BR>By:</FONT></TD>
<TD width="1%"><FONT size=2><BR>&nbsp;</FONT></TD>
<TD align=middle width="45%"><FONT size=2><BR>/s/ Barbara Campbell</FONT><HR noShade><FONT size=2>Barbara Campbell<BR></FONT><FONT size=2><I>Vice President<BR>
</I>(Authorized Officer)</FONT></TD></TR></TABLE>
<P>&nbsp;</P><P>&nbsp;</P><P>&nbsp;</P><P>&nbsp;</P>
<P align=center><FONT size=2>3</FONT></P><HR noShade>
<P>&nbsp;</P><P>&nbsp;</P>
<P align=center><B><FONT size=2>EXHIBIT INDEX</FONT></B></P>
<P align=center>&nbsp;</P><DIV align=center><CENTER>
<TABLE style="BORDER-COLLAPSE: collapse" borderColor=#111111 height=82
cellSpacing=0 cellPadding=0 width=543 border=0>
<TR><TD vAlign=bottom width=163 height=18>
<P align=center><FONT face="Times New Roman" size=2>Exhibit No.</FONT></P></TD>
<TD vAlign=bottom width=748 height=18>
<P align=center><FONT face="Times New Roman" size=2>Description</FONT></P></TD></TR>
<TR><TD vAlign=top width=163 height=19><HR width="90%" color=#000000 SIZE=1></TD>
<TD vAlign=top width=748 height=19><HR width="90%" color=#000000 SIZE=1></TD></TR>
<TR><TD vAlign=top width=163 height=45>
<P align=center><FONT face="Times New Roman" size=2>99.1</FONT></P></TD>
<TD vAlign=top width=748 height=45><P align=center><FONT face="Times New Roman" size=2>
Washington Mutual MSC<br>Mortgage Pass-Through Certificates, Series 2005-RA1<BR>
Monthly Distribution Report for May 2005</FONT></P></TD></TR></TABLE></CENTER></DIV></BODY></HTML>
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934
Date of Report (date of earliest event reported):  May 25, 2005
WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
WASHINGTON MUTUAL MSC MORTGAGE PASS-THROUGH CERTIFICATES
SERIES 2005-RA1
(Exact name of Registrant as specified in its charter)
Delaware
333-103345-64
94-2528990
(State or other jurisdiction
of incorporation)
(Commission File Number)
(I.R.S. Employer
Identification No.)
1201 THIRD AVENUE, WMT 1706
SEATTLE, WASHINGTON 98101
(Address of principal executive offices and Zip Code)
Registrant's telephone number, including area code:
(206) 377-8555
SECTION 8.  OTHER EVENTS
ITEM 8.01  Other Events
This Current Report on Form 8-K relates to the distribution report furnished to certificate holders in connection with the May 2005 distribution.
SECTION 9.    FINANCIAL STATEMENTS AND EXHIBITS
ITEM 9.01 Financial Statements and Exhibits
(a) Not applicable
(b) Not applicable
(c)  Exhibits
Exhibit No.
Description
99.1
Washington Mutual MSC
Mortgage Pass-Through Certificates, Series 2005-RA1
Monthly Distribution Report for May 2005
2
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Date:       May 27, 2005
By:
/s/ Barbara Campbell
Barbara Campbell
Vice President
(Authorized Officer)
3
EXHIBIT INDEX
Exhibit No.
Description
99.1
Washington Mutual MSC
Mortgage Pass-Through Certificates, Series 2005-RA1
Monthly Distribution Report for May 2005