We investigated the value of digital rectal examination, transrectal ultrasonography and prostatic specific antigen (PSA) analysis as aids in general clinical practice and in the early detection of prostate cancer. Of a randomly selected population of 2,400 men 55 to 70 years old who were offered examination with digital rectal examination, transrectal ultrasound and PSA analysis, 1,782 (74%) accepted and prostate cancer was detected in 65 (3.6%). When the transrectal ultrasound results were also considered the detection rate of digital rectal examination (2.3%) was increased by 50% and the number of stage T2A or less tumors was doubled. At reexamination due to markedly high PSA values (7 micrograms/l. or more) only a few additional cancers (5%) were detected. However, it is noteworthy that 80% of the detected cancers were found among the subgroup with abnormal PSA values (4 micrograms/l. or more) and comprising 17% of the study population, which suggests the possibility of selecting a risk group at mass screening. Moreover, the positive predictive value increased from 4% (when only digital rectal examination was positive) to 71% for the combination of positive digital rectal examination, positive transrectal ultrasound and an increased PSA concentration (that is 7 micrograms/l. or greater).