A comparison was performed of the results reported in the literature of chemicals tested in the rat liver foci assay and/or in the strain A lung tumor assay to the results of the chemicals in long-term carcinogenicity bioassays. The rat liver foci assay was sensitive to 69% of 54 compounds found to be carcinogenic in long-term bioassays and the strain A lung tumor assay to 54% of 93 carcinogens. None of the ten compounds found to be noncarcinogenic in long-term bioassays were active in the rat liver foci assay, while seven of 23 non-carcinogens (30%) were active in the lung tumor assay. Ten of the 16 carcinogens negative in the rat liver foci assay are believed to be tumor promoters; 3 are direct-acting alkylating agents (dimethylsulfate, epichlorohydrin, and beta-propiolactone); and the remaining 4 are azobenzene, 1,2-dibromoethane, oxazepam and thioacetamide.