A state-of-information survey concerning health effects of indoor air pollutants in the categories of formaldehyde, volatile organics, radon, particulates, and combustion products has been prepared by the U.S. Environmental Protection Agency's Environmental Criteria and Assessment Office, RTP, N.C. Included in each category are human effects, animal exposure experiments, mutagenicity, and carcinogenicity information. In addition to those health implications associated with each category of pollutants, the problems of measuring exposure to the complex mixtures actually breathed by people in homes is addressed.