In the laboratory, the authors have utilized C3H10T1/2 cells to study the effects of environmental chemicals on mammalian cells. During the course of these studies, they bioassayed a wide variety of chemicals including polycyclic aromatic hydrocarbons, alkylating agents, aromatic amines, azodyes, solvents, pesticides, mycotoxins, carbamates, and nitroaromatics. The results of these studies are summarized. In the present study, the authors evaluated the effects of hexamethylphosphoramide (HMPA). o-toluidine, benzene, safrole, and caprolactam on oncogenic transformation of C3H10T1/2 cells. The original protocol of Reznikoff et al. (1973a) was used with minor variation.