I tried compiling a C# program using mcs after renaming the MS.Net framework supplied mscorlib.dll that's on my machine. mcs could not complete compilation and terminated! Why does mcs need mscorlib.dll? Isn't it supposed to use mono's corlib.dll? The IL dump of the C# code compiled using mcs(without renaming the MS supplied mscorlib.dll) shows references to mscorlib.dll. Thanks bvv