This paper describes programs, established at Mobil Oil Corp., for assessing, managing, and communicating the hazards of petroleum products. Toxicological evaluations must be part of a systematic and integrated program of assessing hazards and risks for man. Test articles are chemically analyzed, and critical animal tests are followed up by mechanistic studies to identify active components and the causes of toxicity. A thorough program evaluates acute and sub-chronic toxicity, carcinogenicity, mutagenicity and reproductive hazards. New tests or modifications to standard tests are developed for the evaluation of complex hydrocarbon mixtures when standard procedures are inadequate. Results of toxicology testing and information on incidence of human exposure provide the basis for risk management decisions.