Kinetics of prostate-specific antigen (PSA) were investigated after manipulation of the prostate in two groups of patients: those treated with digital rectal examination (DRE), and those with needle biopsy. 8 patients had serial PSA measurements to study the effect of DRE (group 1). 7 of 8 patients had PSA baseline values < 10 ng/ml. Blood samples were taken at 1 min, 30 min, 1, 3, 6, 12 and 24 h after DRE. Some patients were further monitored for 5 days with one blood sample taken at the same time each day. Statistically significant increased PSA levels were found after DRE (P < 0.001). Maximal increase was 70%. In most patients, peak levels were found between 30 and 60 min after DRE. Based on the results, it is concluded that after DRE it is prudent to wait 3 days before PSA is determined. 7 patients had serial PSA measurements after transrectal prostate needle biopsy (group 2). PSA sampling was similar as in the previous group. All patients had increased PSA levels after biopsy (range 1.3-9.5-fold). After 5 days, only 2 of 7 patients had returned to baseline levels. We conclude that biopsies of the prostate induce an important and long-lasting PSA elevation.