Quantitative analysis of stray light in optical system is often a burden for optical designers. Ghost images due to multiple reflections on the surfaces of lenses and mirrors must be minimized during the design and optimization phases. Stray light in general must be controlled also during the optomechanical drawings. Already presented at the ICSO 2000 conference (Ref. 1), the CODE V macro software PARASIT makes it possible to have a complete quantitative analysis of the ghost in a few minutes. The possibilities of PARASIT are summarized with emphasis given to recent developments and comparison are given with LightTools. To make a full evaluation of the stray light in general, the possibilities of Light Tools, MATLAB and EXCEL interacting together using the Microsoft Active X protocol are unbeatable, as long as methods and corresponding macros written in EXCEL VBA and MATLAB .m are at the disposal of the optical designer. A short overview of these possibilities are demonstrated in this paper.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.