The authors analyzed 150 patient files (16 controls with no prostatic pathology, 96 patients with benign prostatic hypertrophy (BPH), 38 prostate cancer patients) in an attempt to answer three questions: how should borderline values of PSA be interpreted in patients with BPH; is there a correlation between the Gleason grade and PSA levels in prostate cancer? Should both PSA and PAP concentrations be assayed? All patients underwent digital rectal examination and transrectal ultrasonography (TU), and were assayed for PSA and PAP. All prostate cancer patients had a bone scintigraphy (Bs). In view of the correlation coefficient of 0.391 (p less than 0.001), it can be affirmed that PSA and weight are linearly correlated in BPH (5 g BPH = 1 ng/ml PSA). This lower value of PSA is due to the overevaluation of prostate weight by TU. In contrast, the authors did not find any correlation between the PSA level and the Gleason grade in prostate cancer patients with a negative bone scintiscan. Finally, the sensitivity of PSA was markedly better than that of PAP (75% vs 50%), and no PSA false negative error was corrected by the PAP value.