Subcutaneous tumor induction with three dose levels of 3-methylcholanthrene (MCA), benzo[a]pyrene (BP), and 7,12-dimethylbenz[a]anthracene (DMBA) in two vehicles was studied in C3H/Anf Cum, C57BL/6 Cum, DBA/2J, and (C57BLXC3H/Anf)F1 (BC3F1/Cum) mice. Median tumor dose levels were significantly lower when the three carcinogens were suspended in trioctanoin. When beeswax: trioctanoin (B:T) was used as a vehicle, the three carcinogens differed in their abilities to be absorbed or solubilized from the vehicle by the three strains of mice and the hybrid. In C3H/Anf mice, BP in B:T failed to produce tumors. In BC3F1 mice, no tumors were produced by MCA, BP, or DMBA in B:T. In C57BL/6 mice, no tumors were produced with DMBA or MCA in B:T. In DBA/2 mice, no tumors were produced by BP or MCA in B:T. These results indicated that the interpretation of tumor induction results obtained with B:T vehicle may be related to the conditions of bioassay rather than to the carcinogenic potential of a compound.