Within a study on diet as a risk factor for fibrocystic disease and breast cancer, 68 patients with breast cancer, aged from 40 to 59, participating in the National Breast Screening Study in Montreal, were compared to 340 patients with fibrocystic disease and to 343 controls. The personal and family history was collected from medical records and completed by an interview. The nutritional assessment was done by a food frequency questionnaire with a special attention to the quantity and quality of fat, vitamins A, C, E, as well as life style habits. The cancer patients were significantly heavier (64.9 vs. 60.8 kg), had higher body mass index (24.9 vs. 23.4), menstrual cycle more often irregular, later menopause (47.5 vs. 44.5 years), and shorter school attendance (10.3 vs. 12.6 years). No significant differences were found in the use of contraceptives, menopausal hormones, analgesics and tobacco, marital status, number of pregnancies and children, age at menarche, duration of menstrual cycle, and the age at the first pregnancy. The cancer patients consumed significantly more poultry, fish, pastry, margarine, and alcohol and less milk, raw vegetables, pastas, sugar, butter, and coffee.