In order to determine to the effect of benzo[a]pyrene (BaP) on breast cancer risk we conducted a case-control study in the time period 1996-2004. The study included 1,098 participants (460 cases and 638 controls). All the patients were drawn from the four major hospitals in Montevideo, Uruguay. Statistical analysis was performedusing unconditional multiple logistic regression and the models included age, residence, urban/rural status, education, monthly income, body mass index, menopausal status, age at menarche, parity, smoking index, alcohol drinking, mate consumption, total energy, total vegetables and fruits, and BaP intake. The highest vs. the lowest quartile of BaP intake (OR 2.0, 95 % CI 1.2-3.3) was significantly associated with breast cancer risk. Alcohol drinking was also directly associated with breast cancer risk (OR 1.63, 95 % CI 1.19-2.23) and the joint effect of BaP and alcohol drinking showed an elevated risk of the disease (OR 3.32, 95 % CI 2.17-5.06). The present study suggests that elevated consumption of BaP could play an important role in the etiology of breast cancer. This effect is enhanced by the intake of alcohol.