I am interesting in knowing (understanding) the difficulties in programming MPI when one of more processes within a process group is written in C and one or more is written in FORTRAN. And to mix it up a bit, let's also assume that some of the processes (C or FORTRAN) are using mixed native word sizes (32/64 bit). I have been asked to write some benchmark code that exposes these issues. If there is any code that illustrates these issues please send a link. Thanks Mike Stokes