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The change of the staple diet of Black South Africans from sorghum to maize (corn) is the cause of the epidemic of squamous carcinoma of the oesophagus. For many years sorghum was the staple diet of Black South Africans. From approximately the early part of the twentieth century, maize gradually replaced sorghum. Squamous carcinoma of the oesophagus was infrequent in the first half of the twentieth century, rising slowly to current epidemic proportions. Fusarium fungi grow freely on maize, producing fumonisins, which reduce nitrates to nitrites and synthesise cancer-producing nitrosamines. Nitrosamines are the presumed carcinogens. Fusarium fungi do not grow well on sorghum, the production of fumonisin from sorghum being two orders of magnitude lower than maize. The higher incidence of oesophageal cancer in Black males is ascribed to their greater consumption of traditional beer, which is produced by fermenting maize. Patients with oesophageal cancer consume more beer than controls. Countries in Africa, in which the staple food is sorghum, have a low incidence of squamous carcinoma of the oesophagus. Crops from various parts of the country should be examined for Fusarium fungi and nitrosamines. The nitrosamine content of traditional beer should be assessed. If nitrosamines are detected, their carcinogenic potential should be studied experimentally. Should these tests prove positive, it would be vital to break the Fusarium-nitrosamine-cancer chain.