AbstractMany old Fortran programs are still heavily used though often very inefficient in use of computer resources. This paper suggests a graphical approach to understanding an existing program and several techniques for speeding up a program through improved event handling routines, faster numerical methods, and better file handling. A detailed case study is presented of a Fortran program that was significantly speeded up by relatively simple changes to its event handling routines that reduced queue handling from more than 30% of total run time to less than 2%.