Computer-assisted sperm analysis (CASA) systems are becoming more widely used. With this spread of technology come more data from toxicology studies, designed to determine if treatment with putative toxicants affects sperm motion parameters. While these CASA methods provide us with more ways to evaluate toxicity, and thus perhaps increase the chances of successfully protecting human health, there is also a greater likelihood that different laboratories will use different methods of collecting data on sperm motility. Different systems and different methods will produce data that are difficult to compare. In a prospective attempt to address this issue of comparability and limit the problems, a group of individuals using CASA systems to analyze rat sperm motility convened to discuss methodologic issues, share data, and tried to reach a consensus about methods for performing these studies. The manuscript shares those meetings and data in the hope that common methods will enhance inter-laboratory comparisons. (Copyright (c) 1992 Pergamon Press Ltd.)