Unfortunatly the proposed solutions didn't work after all (It worked once, I think, but.) Here again the problem: glasPng.dll is a Delphi dll with the function getPngVersion in it. Calling convention is stdCall. I want to use this dll. The code: {-# LANGUAGE ForeignFunctionInterface #-} module Main( main ) where import Control.Monad import Foreign.C import Foreign.Marshal.Alloc import Foreign.Marshal.Array import System.Win32.Types foreign import stdcall "getPngVersion" getPngDllVersion :: IO CString main :: IO () main = do s <- getPngDllVersion putStrLn (show s) glasPng.dll is in the Windows path (I've checked it). If I compile with ghc --make testGlasPng.hs -lglasPng I get: ..\ld.exe: cannot find -lglasPng. Collect 2: ld returned 1 exit status. Ld can't find lglasPng (with the l in front, does it trim the l?). Why? Okay I try ghc --make testGlasPng.hs -L<path to glasPng.dll> I get: testGlasPng.o: fake: (.text + 0x82) :undefined reference to 'getPngVersion@0'. I think it has found the dll, but it complains the function is not in the dll. But TDump and Dll export viewer say getPngVersion is in the dll. I run ghc on a 64 bits computer. The dll is 32 bits. Is that the problem? What can I do? Kees