A case-control study on dietary factors and colorectal adenomas was conducted in the island of Majorca, Spain, from April 1987 to February 1990. Subjects were interviewed using a food frequency questionnaire. Nutrient and caloric intake was estimated using local food composition tables. The risk of colorectal adenomas was related to the consumption of sugar and pastries. Consumption of vegetables was highly protective, irrespective of the cooking procedures. Analyses by nutrients identified as protective factors fiber from fruits and vegetables, magnesium and zinc, and vitamins C, B6 and folic acid. No excess risk was found for alcohol drinking, intake of saturated fats or animal protein. Of the non-dietary factors, sedentariness in the work-place and urban residence were the only risk factors identified.