Fraser P (Epidemiological Monitoring Unit, London School of Hygiene and Tropical Medicine, Keppel Street (Gower Street) London WC1, England), Chilvers C, Beral V and Hill M J. Nitrate and human cancer: a review of the evidence. International Journal of Epidemiology 1980, 9: 3–11. Nitrites, derived mainly from ingested nitrates, may react in vivo with secondary nitrogen compounds occurring naturally in certain foods to form N-nitroso compounds, which are potent carcinogens in laboratory animals. This paper reviews the mechanism of their formation and the evidence from epidemiological studies that high nitrate ingestion is involved in the aetiology of human cancer.