The current epidemiological transition in less developed countries is resulting in an epidemic of chronic diseases, with cancer being the second most common cause of mortality. The evidence linking diet to the development of cancer is based largely on epidemiological analysis of the relationships of the frequency of different cancers to data on food consumption. Cohort results have made clearer the link between diet and cancer, as have data on a number of biological mechanisms. Based on the available data, recommendations on dietary practices that may prevent cancer have been published recently by the American Institute for Cancer Research and the World Cancer Research Fund. Key recommendations are: diet should be based on plant products; 400 g of vegetables and fruits, to provide more than 10% of energy, should be consumed daily; cereals, legumes and tubers should provide at least 50% of energy, and sugars less than 10%; no more than 80 g of meat should be consumed, preferably fish or poultry, and limited amounts that are cured or smoked; fat intake should be limited to no more than 30% of energy, with a predominance of monounsaturated and polyunsaturated forms; total salt consumption should be less than 6 g; perishable foods should be kept frozen or refrigerated and consumed promptly; foods should be cooked at low temperatures, better to be boiled or steamed rather than fried or grilled; alcohol should not exceed 2 drinks a day. In addition to these dietary guidelines, cancer prevention may be achieved by not smoking, by avoiding excess weight, and by increasing physical activity, including half an hour of exercise and 4 hr not resting in a chair or bed.