Epidemiological studies have suggested that aspirin may have a protective effect against prostate cancer, but the evidence is still limited and inconsistent. The role of aspirin in prostate cancer risk was analysed in a multicentric case-control study conducted in Italy between 1991 and 2002, including 1261 incident cases of carcinoma of the prostate and 1131 hospital controls. A total of 115 (9.1%) cases versus 90 (8.0%) controls reported regular aspirin use. The multivariate odds ratio (OR) for regular aspirin users was 1.10 (95% confidence interval (95% CI) 0.81-1.50). No relation was found with duration of use (OR = 1.03 for <5 years, and 1.17 for > or =5 years) and time since first use (OR = 1.03 for <10 years, and 1.35 for > or =10 years). These findings do not support a protective role of regular aspirin use on prostate cancer risk.