I am having some difficulties writing double precision variables using gfortran in 64-bit mode: source code is double precision d d=0. write(0,*) d end $ /usr/local/usr/bin/gfortran-4.0 -m64 -o pmain2 pmain2.f -L/usr/local/usr/lib $ ./pmain2 Illegal instruction If I define d to be integer, then I am able to print it with no problem. Configuration for this gfortran: $ /usr/local/usr/bin/gfortran-4.0 -v Using built-in specs. Target: powerpc-apple-darwin8 Configured with: /Build/apple/gcc/build/obj/src/configure --disable-checking -enable-werror --prefix=/usr --mandir=/share/ man --enable-languages=c,objc,c+ +,obj-c++,f95 --program-transform-name=/^[cg][^.-]*$/s/$/-4.0/ --with-gxx-include-dir=/include/c++/4.0.0 --build=powerpc- apple-darwin8 --host=powerpc-apple- darwin8 --target=powerpc-apple-darwin8 Thread model: posix gcc version 4.0.1 (Apple Computer, Inc. build 5224) Thank you for your help Roger Ghanem Roger Ghanem 254C Kaprielian Hall University of Southern California Los Angeles, CA 90089 Tel: 213 740 9528 Fax: 213 740 2037