This article summarises the experience and results of different prostate carcinoma screening projects using total prostate specific antigen (PSA) and per cent free PSA as the initial test. Of the 21078 volunteers 1618 (8%) had elevated PSA levels. Of these men 778 (48%) underwent biopsies; 197 (25%) biopsies were positive for prostate carcinoma and 135 (17%) underwent radical prostatectomy. 95 were found to be organ-confined. A PSA cut-off of 2.5 ng/ml in men aged 45-49 years and of 3.5 ng/ml in men aged 50-59 years resulted in an 8% increase in the detection rate of organ-confined disease. 284/2272 men (13%) had elevated PSA levels and prostate carcinoma was detected in 62 men (3%). All patients underwent radical prostatectomy and histological examination revealed organ-confined tumour in all but 8 men. 98/340 men (29%) had biopsies positive for carcinoma; 28 of these patients (29%) had carcinoma that originated in the transition zone only. In the retrospective study, receiver operating characteristic curve analysis showed that by using a per cent free PSA of less than 18% as a biopsy criterion, 37% of the negative biopsies could be eliminated although 94% of all carcinomas would still be detected. In the first prospective study, 106/158 men (67%) with elevated PSA levels below 10.0 ng/ml were further evaluated and 37 (35%) prostate carcinomas were detected. By using a per cent free PSA of <22% as a biopsy criterion, 30% of the negative biopsies could be eliminated although 98% of the carcinomas would still be detected. In the second prospective study, 120/465 men (26%) with total PSA levels between 1.25 and 6.49 ng/ml and a per cent free PSA<18% were further evaluated and 27 (23%) were found to have prostate carcinomas. Receiver operating characteristic curve analysis for PSA transition zone (TZ) density showed that by using a PSA transition zone density of >22 ng/ml/cc as a biopsy criterion, 24.4% of negative biopsies could be avoided without missing a single carcinoma. In the prescreening era the incidence of T1a Grade 1 and 2 carcinomas was 3.1% and the incidence of T1a and T1b Grade 3 carcinoma was 2.3% whereas in the years after the establishment of PSA-based screening the incidence was 4.6 and 1.03% respectively. The rate of organ-confined tumours increased from 28.7% in 1993 to 65.7% in 1997. In this evaluation a new approach, to proceed with a prostate biopsy based upon the individual risk of having prostate cancer rather than a single PSA cut-off point was developed. High total PSA levels, PSA density and PSA transition zone density correlated significantly with high Gleason scores, capsular penetration, a high percentage of cancer in the prostatectomy specimen and a high cancer volume. In this evaluation all of the 95 patients with PSA levels below 3.99 ng/ml who underwent radical prostatectomy showed clinically significant, organ-confined prostate cancer with negative surgical margins. The results of this evaluation suggest that older men have larger tumour volumes compared with younger men with the same PSA levels. These data suggest that PSA-based screening with low PSA cut-off values increase the detection rate of clinically significant, organ confined and potentially curable prostate cancer. Per cent free PSA and PSA transition zone density provide an additional diagnostic benefit over total PSA.