This paper reviews the results of a series of efforts to develop structure-activity models for slow-reacting chemicals and olefins whose toxicity may be enhanced by the ultraviolet radiation. Photoinduced toxicity of 14 compounds was found to be a different result of competing factors of structure, having carbon-carbon double bonds. To mimic the biological consequences of photooxidative damage in mammalian cells, the photochemical mutagenicith of 14 chemicals was tested in the CAS. Simple olefins were photochemically mutagenic or carcinogenic with irradiation, increasing the alkylating activity from zero level to 0.87(abs/gram) for styrene, 0.25 for 1-butene, 0.11 for 1-hexene, respectively, whereas no photochemical mutagenicity was observed with 1-octene in the absence of the CAS. Oxide compounds, however, showed a decreasing trend of photoalkylating activities in the presence or absence of the CAS. We found that the structure-activity relationship was not applicable to our data.