A case-control study was conducted to analyze the possible role of diet on the incidence of breast cancer in a group of 275 women (139 cases and 136 controls) recruited from three hospital populations (Madrid, Mérida, and Santiago de Compostela). The retrospective intake of foods was studied by a modified dietary history; from this the intake of energy, nutrients, fiber, and alcohol was derived. Intake of oils and fats was significantly higher among cases, which translates into a higher intake of lipids and vitamin E. In contrast, intake of vitamin D and legumes was significantly lower. No differences were observed regarding other foods and nutrients between cases and controls. The estimate of the odds ratio as a relative risk measure for breast cancer, adjusted and unadjusted for total energy, indicates that intake of cereals and legumes, proteins, carbohydrates and fiber is apparently a protective factor, whereas an excessive intake of meat, oils and fats and a lipid intake higher than 46% of the total caloric intake or poly-unsaturated fatty acids higher than 15 g would be a risk factor for this pathology.