One Copy&Paste-error. The first DllImport was not byte[] but IntPtr :) [...] Because it is a "const void*" I used the following DllImport statement [ DllImport(lib) ] static extern void multiDimArrayTest( IntPtr elems ); and this methode call multiDimArrayTest( GCHandle.Alloc( mdArray, GCHandleType.Pinned).AddrOfPinnedObject() ); [...] Tim