The purpose of this study was to evaluate the mutagenic potential of the test substance, Paraffinic Oil 78-9-70 SUS/100 degrees F, using four mutational assays: the Ames Test, the suspension of modification of the Ames Test, the Mouse Lymphoma Test and the In Vivo Bone Marrow Cytogenetic Assay. The Ames Test is a bacterial mutagencity assay utilizing selected strains of Salmonella typhimurium. The organisms are exposed to varying concentrations of the test agent both with and without metabolic activation. The suspension modification of the Ames Test uses strains of s. typhimurium; however, the organisms are exposed in suspension to varying concentrations of the test agent for a specified time and temperature without the agar overlay. The agar is added at the end of the incubation period and the test is conducted both with and without metabolic activation. The Mouse Lymphoma test is a mammalian cell assay utilizing the L5178Y mouse lymphoma cell line. The cells are exposed to varying concentrations of the test agent both with and without metabolic activation. The assay measures the mutation frequency of the specific locus for thymidine kinase (TK). The In Vivo Cytogenetics Assay evaluates the mutagenics potential of a test material as manifested by the production of cytogenetic abnormalities such as deletions, exchanges, rings and breaks in the chromosomes of bone marrow cells of rats receiving the test material.