AbstractThis review presents a critical, select evaluation of the amount and type of fat or fiber in nutritional carcinogenesis, with the emphasis being on cancer development in the mammary gland and large bowel. The role of nitrate and nitrosation is described in relation to risk for cancers of the head and neck (especially the esophagus) and cancers of the stomach and the liver. Systematic tests of increasing complexity to delineate possible carcinogenic risk in food additives and contaminants are described. Specific recommendations stemming from these evaluations are made as to dietary recommendations designed to reduce cancer risk.