1.1 ,This test method covers a microbiological test procedure based upon the Salmonella mutagenesis assay of Ames et al. (1)2 (see also Maron et al. (2)). It can be used as a screening technique to detect the presence of potential dermal carcinogens in virgin base oils used in the formulation of metalworking oils. Persons who perform this test should be well versed in the conduct of the Ames test and conversant with the physical and chemical properties of petroleum products.