The method for determination of angiotensin-converting enzyme activity in human spermatozoa and seminal plasma was developed. The number of total and active-motile spermatozoa was shown to be lower in Chernobyl victims than in healthy donors. The specific activity of angiotensin-converting enzyme in spermatozoa from Chernobyl victims was 12 times higher than that in donors. Similar results, although to a lesser extent, were observed in patients with chronic prostatitis. In contrast, the enzyme activity in blood serum and seminal plasma was identical for all subjects investigated.