Available information on the carcinogenicity of formaldehyde (50000) is reviewed based on epidemiological and experimental studies. Formaldehyde exposure in the workplace as currently regulated by federal standards is not to exceed an 8 hour time weighted average of 3 parts per million (ppm), 5ppm ceiling and a 10ppm short term exposure. In measuring exposure levels, it is crucial to select the proper sampling equipment, as it must be consistent with the type of environment to be sampled and the anticipated concentration levels. The biochemistry, metabolism, and pharmacokinetics of formaldehyde in the human body are reviewed. Carcinogenic and mutagenic evidence is presented, and the mechanisms of genotoxicity are noted. Areas also reviewed include the results of chronic formaldehyde inhalation bioassays, physiologic responses to sensory irritation, role of the nasal mucociliary apparatus, cell proliferation in response to cytotoxicity, dose response relationships and species differences relevant to data transfer from animal to man, review of epidemiologic studies of cancer in relation to formaldehyde exposure, and recommendations for further research. These recommendations include studies to increase understanding of dose considerations, molecular mechanism of action, carcinogen associated tissue responses, tumorigenic mechanisms and dose response, as well as epidemiologic studies and risk assessment.