Efforts in the area of risk assessment have concentrated primarily on cancer as an outcome. However, attention is now being directed toward the development of strategies for assessing risk to other target systems. The Reproductive Effects Assessment Group in the Office of Health and Environmental Assessment, U.S. EPA, is involved extensively in that effort in the areas of developmental and reproductive toxicology and mutagenicity. This group is currently preparing risk assessment guidelines for the male and female reproductive systems. Some of the issues associated with hazard identification and dose-response assessment with respect to male reproductive toxicity are discussed.