Human cancer is generally considered to be related to environmental factors. 1 - 2 Dietary factors, including carcinogens in the diet, seem to be very important in the development of cancers. 13 Charred parts of broiled fish and beefsteak were first demonstrated in our laboratory to be mutagenic to Salmonella typhimurium TA98 and TA100 with S9 mix. 4 - 5 Subsequently, a series of heterocyclic amines were isolated from pyrolysates of amino acids and proteins and were shown to be highly mutagenic. 6 9 These heterocyclic amines have also been shown to be carcinogenic in mice and rats. This chapter summarizes available data on the carcinogenicities of these heterocyclic amines.