It is estimated that reproductive toxicity evaluations have been carried out on only 4,000 of the approx 84,000 chemicals for which there is potential workplace exposure. It would be prohibitively costly and time consuming to screen all chemicals for possible effects on reproduction. A prioritization process to rank reproductive toxicants identified by the National Toxicology Program (NTP) has been formulated by an expert panel (Moorman et al ., 2000). Prioritization was based on potency in animal toxicity studies and size of the potential exposed population. NTP utilizes the reproductive assessment by continuous breeding (RACB) protocol to evaluate reproductive toxicity. This testing approach as well as other animal testing systems will be presented. Endpoints in reproductive toxicity tests will be reviewed in context of the processes underlying reproduction and development. Key elements in minimizing potential for human reproductive harm are effective screening mechanisms, quality exposure assessment, mechanism of action studies and occupational health field studies. Selected chemicals with high potential for reproductive toxicity and for which a significant data set exists will be discussed.