In recent years a lot of efforts were made to characterize laser beams and to describe their propagation in optical systems. More than two years one working group of the International Organization for Standardization (ISO) worked in this field and has proposed a procedure to measure beam width and beam divergence1. The Optical and Quantum Electronics Journal will publish a special issue on laser beam quality this year2. What a waste of time for a single parameter one might think. What are the problems, then?