The importance of priority setting for reproductive research and the priority system NIOSH has used to nominate and evaluate epidemiologic studies within the Division of Surveillance, Hazard Evaluations, and Field Studies were described. Current efforts to develop a more systematic method of nominating chemicals for study were delineated. Typically NIOSH has chosen chemicals and populations to study through a two step process. The first step involved the nomination of a chemical or population by one of several sources such as toxicologists, representatives of labor or management, or NIOSH researchers. The second step involved an evaluation of the nomination on its scientific merit and practicality of executing a study. High standings of priority have been afforded to agents found to have a very toxic effect on reproduction in animals, chemicals that affect a large number of workers, projects that would aid in setting exposure limits, studies that might confirm or refute previous studies, and feasibility studies which typically precede large scale research projects. Medium priority has been extended to projects which evaluate the risk of a known reproduction hazard below the established standards, to projects designed to assess reproductive health of defined groups with mixed exposures, and projects where there was no evidence of toxicity but which were of public concern. Low priorities have been given to projects designed to document or duplicate a well established finding or projects which would not have a good probability of affecting general public health.