I met this problem before. There is a GLOBAL TXTLIB statement in the PROFILE EXEC of CMSUSER that sets the libraries for the compilers. The GCCLIB and FORTLIB are in the list but they both contain a SQRT function. Because GCCLIB comes first in the list, the SQRT of that library is the one used with your FORTRAN program, and it is the wrong one. Peter, however, first set the GLOBAL TXTLIB to FORTLIB only which results in the right SQRT being used at execution.