Objectives. To measure the impact of ejaculation on the serum levels of prostate-specific antigen (PSA) in a prostate cancer-screening population.

Methods. Questionnaires regarding history of ejaculation were administered to all participants in a prostate cancer-screening trial. Two groups were analyzed. The first cohort consisted of 618 men who answered the questionnaire, and their serum PSA values were compared according to time since last ejaculation. The second cohort consisted of 89 volunteers who agreed to come back for a postejaculation PSA for whom a before and after ejaculation PSA was measured. Regression analysis was conducted between change in PSA and time since ejaculation as well as in the magnitude of change and baseline PSA.

Results. The mean (±SD) age of the studied population was 60.43 ± 9.23 years. A non-statistically significant difference in PSA levels was observed for either cohort. For the 89 volunteers the mean PSA change after ejaculation was −0.62 ± 0.75 (not significant). Initially, the PSA decreased, and then after 9 hours a steady increase was observed. After 12 hours, the serum PSA returns to baseline. The regression analysis between baseline PSA and magnitude of change showed a strong correlation (r = .557). The higher the baseline PSA, the greater the magnitude of change.

Conclusions. For the total screened population, ejaculation has no clinically significant effect. Men should not be asked to abstain from sexual activities before a PSA-screening test.