Prostate Specific Antigen (PSA) is the most important marker of prostate diseases actually available. The aim of this study was to evaluate the relations between aging, PSA and prostatic volume's increase, and whether these relations justify the adoption of different normality ranges of PSA in the elderly. We considered 285 patients aged over 60 years (mean age 69.01 years), with Benign Prostatic Hyperplasia (BPH) and absence of malignant prostatic disease, prostatic phlogosis and absuntion of drugs that can influence the PSA's levels in the serum. Patients underwent PSA, digital rectal exploration and transrectal ultrasonography, with determination of the three prostatic diameters, of the prostatic volume by the ellipsoid formula and of the maximum adenoma diameter; PSA was determined in all patients and PSA free in those with total PSA > 4 ng/ml; the PSA density was calculated. We found that age does not correlate with PSA and is poorly correlated with prostatic volume (p < 0.05); on the contrary, PSA values are strongly related with prostatic volume and maximum diameter of adenoma (p < 0.01). Mean free PSA value was 16.3 +/- 5.99%, and most of patients had values in the so-called grey zone of discrimination between benignity and malignity. We conclude that in elderly patients with volume. These results suggest the possibility to consider as indicative of benignity also total PSA values between 4 and 10 ng/ml, when they are associated with a significative prostatic volume's increase and with free PSA greater than 10%.