Polycyclic organic matter (POM) is emitted from a variety of sources in the environment. Evidence of the carcinogenicity of emissions from coke production, motor vehicles (includes tire wear), asphalt roofing, paving, and air blowing, catalytic cracking residential coal combustion, industrial/utility coal combustion, carbon black, and iron and steel processes is presented. The contribution of the POM fraction to the carcinogenicity of the mixture is evaluated for gasoline engine exhaust condensate and coal combustion effluent and appears to contribute the majority of the carcinogenic potential for those mixtures. Evidence of the mutagenicity of emissions from coke production, motor vehicles (including tire wear), industrial/utility coal combustion, carbon black, iron and steel processes, forest fires and open burning, residential solid fuel (wood) combustion, commercial and other incineration, commercial/industrial oil combustion, residential oil combustion, and asphalt roofing, paving, and air blowing is also presented. The problem in the use of a chemical surrogate to sample for POM-containing emissions is discussed. A discussion of the problems in evaluating the carcinogenic potential of different POM-containing mixtures is also presented.