['Body mass index (BMI) may alter serum prostate specific antigen (PSA) and percent free PSA (%fPSA) and may mask the risk of prostate cancer. We investigated the relationship between BMI and PSA or %fPSA.', 'Height, weight, PSA and %fPSA were assessed in 616 consecutive screened men without prostate cancer. Continuously coded and categorised BMI was studied. Statistical analyses consisted of ANOVA, linear regression, bivariate and partial correlations.', 'Median age was 57 years. Median PSA was 1.0 and median %fPSA was 26. Median BMI was 25.8 kg/m(2). Neither continuously coded nor categorised BMI correlated with either PSA or %fPSA in unadjusted or age-adjusted analyses (all p values > or = 0.3).'] Does body mass index predict prostate-specific antigen or percent free prostate-specific antigen in men undergoing prostate cancer screening?