Levels of retinol, beta carotene, and alpha tocopherol were assayed by high performance liquid chromatography (HPLC) in serum from subjects with clinical prostatic cancer (n = 94), focal prostatic cancer (n = 40), benign prostatic hyperplasia (n = 130), and from hospital controls (n = 130). Levels of beta carotene and alpha tocopherol varied for prostatic cancer patients by disease stage and by the period in the treatment sequence when blood was collected. This made any assessment of their association with prostatic cancer risk difficult. The mean level of serum retinol was significantly lower (P less than 0.05) in prostatic cancer patients than in the controls. For serum retinol this difference did not appear to be attributable to age, stage of disease, period in which the blood was collected, or to several other potentially confounding factors. When the serum retinol level was considered in quintile classes, there was a statistically significant (P less than 0.05) trend of increased prostatic cancer risk associated with decreasing serum retinol levels.