http://extended64.com/blogs/news/archive/2009/05/10/tail-call-improvements-in-net-framework-4.aspxFirst a little background reading before going into tail call improvements in CLR 4 - David Broman did an excellent job at covering the basics in his post here: http://blogs.msdn.com/davbr/archive/2007/06/20/enter-leave-tailcall-hooks-part-2-tall-talesenCommunityServer 2008 SP1 (Build: 30619.63)