On the basis of 150 patients (16 controls with no disease of the prostate, 96 cases of benign prostatic hypertrophy (BPH) and 38 cases of carcinoma of the prostate (CP)), the authors intended to answer 3 questions: How can the borderline values of PSA in BPH be interpreted? Is there a correlation between the Gleason and PSA values in carcinomas? Should the simultaneous measurements of PSA and PAP be continued? All patients were examined with a rectal touch, transrectal echography (TRE) and PAS and PAP assays. All CP were examined with bone radionuclide scanning (BR). The correlation coefficient being 0.391 (p 0.001), the PSA value and prostatic weight can be regarded as linearly correlated in BPH (5 g BPH = 1 ng/ml PSA). This lower value of PSA is linked with the increase produced by TRE in the assessment of prostatic weight. On the other hand, the authors did no observe a correlation between the PSA and the Glisson grade in carcinomas with negative BR. Lastly, the sensitivity of PSA is noticeably higher than that of PAP (75% vs. 50%), and no false negative finding with PSA was corrected by PAP measurements.