An IDL process can directly initialize Fortran processing. And IDL processing fcan be initialized rom a C program, from a Java program (starting in IDL 6.3) or through a system shell call to the 'idl' executable. There is, however, no direct interface from Fortran to IDL. You would have to know how to interface Fortran to either a C program, a Java program or to file system executables in order to initialize the IDL process. Once initialized an IDL program could communicate with a Fortran process via: - SOCKETs - The file system - "shared memory" (see SHMMAP in IDL Online Help) if not directly through the C or Java intermediate interface program. I am no expert in Fortran, but I am pretty sure these are all the interface options. They probably all require a fair amount of expertise in Fortran. James Jones