Man may be exposed to a hazard of carcinogenic nitrosamines and N-nitroso compounds on two accounts: one by ingesting the compounds preformed in food and the other by synthesizing the compounds in the stomach from nitrite and N-nitrosatable compounds which may be ingested as natural constituents of food, drugs, and food additives. Synthesis of the compounds from nitrite and amines or amides has been demonstrated in vitro with simulated gastric conditions and in vivo in animals.