Factors affecting the design of an epidemiologic study assessing possible health effects from chemical waste disposal sites are reviewed. Such epidemiologic studies will most likely be prompted either by a known release of chemicals into the environment around the site, or by an unusual disease cluster in a population near the site. In the latter situation, a method for evaluating the health effects is needed, and one possible approach is discussed. In the former situation, it may not be obvious what health outcomes are relevant. Reported associations between health effects and chemicals in humans were reviewed. Studies from the occupational and environmental literature were classified by chemical and target organ affected and presented in tabular form. No attempt was made to critically evaluate the quality of evidence for each health effect, although bibliographic documentation was provided where possible. Episodes of chemical contamination of food, drinking water and other media were also reviewed and presented in a separate table. The organ sites likely to be affected by toxic chemicals from waste disposal sites depend heavily on the route of exposure and the dose that is received. Ingestion is the most frequently reported route of exposure in episodes of environmental contamination. These have affected the hepatic, renal, hematopoietic, reproductive, and central nervous systems. The type and severity of effects were dose-dependent. Direct skin contact is important in the occupational environment where dermal and central nervous system effects have been reported but seems less likely as a route of exposure for populations around waste disposal sites. Inhalation, unless at relative high concentrations or as a result of fire, is unlikely to be important, although hematopoietic, reproductive, and central nervous system effects have been reported in occupational studies.