Linear models of risk assessment may be appropriate for chemicals that are initiators of carcinogenesis while threshold models of risk assessment have been proposed for promoters. The proper risk assessment model for the regulation for promoters of carcinogenesis remains an active area of research and controversy. Published dose-response curves of promoters of multi-stage carcinogenesis were selected which met the combined criteria of long study times, multiple doses and low doses. In rat liver 12 dose-response studies of 7 different promoters were selected, while in mouse skin 10 dose-reponse studies of 4 promoters were chosen. The dose-response relationships are presented on the basis of either moles of promoter, percent of the fully effective promoting dose or percent of the acute oral rat LD50.