Background: Epidemiological studies suggest a relation between breast cancer, diet and life styles. Aim: To analyze the association between food patterns, obesity, smoking, alcohol consumption and breast cancer risk in women of Santiago. Patients and methods: A case-control study design (170 cases and 340 controls), matched by age and sex, was used. Through a food frequency questionnaire the average daily intake of vegetables, fruits, ß-carotene, vitamin A, C, E and fiber was analyzed. Other exposures to non-nutritional risks (parity, smoking, cancer history) were also studied. Conditional logistic regression was calculated to determine the odds ratio associated with variations in food and nutrient intake and nonnutritional factors. Results: Cases had a greater BMI and a higher prevalence of obesity than controls (p< 0.02). No differences were observed in either group food patterns. The ORs for breast cancer associated with obesity and alcohol consumption were 1.65 (95% CI 1.06-2.64) and 1.61 (95% CI 1.06-2.54) respectively (p< 0.05). Multiparity had a protective effect with 0.66 less risk (95% CI 0.44-0.99). No protective effect associated to a greater intake of vegetables, fruits or natural antioxidants was observed. Multivariate analysis model disclosed obesity as a risk factor (OR 1.79, p< 0.02) and parity ³ 4 as protective (OR 0.62, p<0.02). Conclusions: This study does not support a protective role for natural antioxidants against breast cancer but indicate a weakassociation with obesity.