Prostate specific antigen (PSA) has been shown to be useful alone and in conjunction with other tests in the diagnosis of prostatic carcinoma. Previously, we demonstrated that a PSA level of greater than 4.0 ng./ml. as the initial diagnostic test in a screening population results in a detection rate of 2.6 and positive predictive value of 30.5. In the present investigation we performed digital rectal examination and transrectal ultrasound as well as ultrasound guided biopsy in men who in the initial year of the screening study had a PSA level of less than 4.0 ng./ml. but on evaluation 1 year later they had a 20% increase in the PSA level. A total of 701 subjects returned for year 2 of the protocol and 260 (37.1%) demonstrated more than a 20% increase in PSA value. Biopsy was performed in 82 men and carcinoma was detected in 14 (17.1%). Of the men with carcinoma 12 had a second year PSA level of less than 4.0 ng./ml. Radical prostatectomy was performed in 8 patients, 7 of whom had organ confined disease or tumor penetrating the capsule with negative margins. We conclude that a 20% annual change in PSA level may identify men at significant risk for prostatic carcinoma and that patients so identified have favorable pathological stage.