 <p><code>@m_UserIdList</code> is a <code>VARCHAR(500)</code>, not a list of values, so this will not work. You can try and parse the passed in string into a table (and there are plenty of ways of doing so - just search this site).</p> <p>However, since you are using SQL Server 2008, you should take a look at <a href="http://msdn.microsoft.com/en-us/library/bb510489.aspx" rel="nofollow">table valued parameters</a> - these allow you to pass a table of values to a stored procedure.</p>