Over the last decade PSA has been widely acknowledged to be a very sensitive and specific marker of prostatic tumour pathologies. This paper reports the authors' experience relating to the use of PSA in the early diagnosis of prostatic heteroplasia on the basis of results obtained in a study performed in 805 dysuric patients who underwent rectal exploration and CAT. Echo-guided prostate biopsy according to Hodge was performed in 212 (26.4%) out of 805 patients and adenocarcinoma was found in 55 cases (25.9%). PSA ranged between 10-198 ng/ml in 42 out of 212 patients, between 4-10 ng/ml in 60, and was below 4 ng/ml in 110. In addition, PSAd was assayed in all patients with PSA < 10 mg/ml. Having established the cutoff of PSA at 10 ng/ml, it was found that some heteroplasia, above all at the initial sage, presented normal PSA blood values. In fact, in 8 cases, equivalent to 14.5% of the neoplasias diagnosed, values were under 4 ng/ml, and in 5 cases, equivalent to 9%, they ranged between 4-10 ng/ml. This finding showed that the threshold value of 10 ng/ml gives PSA a high specificity, but a lower sensitivity in the early diagnosis of prostatic adenocarcinoma. Moreover, the analysis of PSA-density does not significantly allow the diagnosis of a larger number of heteroplasias: in fact, out of 13 cases of adenocarcinoma with PSA < 10 ng/ml, PSAd was only > 0.15 in 2 patients. Therefore, in line with the data reported in the literature, the authors consider that PSA assay represents a sensitive and specific screening method for prostatic tumour pathologies in symptomatic patients, but in order to obtain an early diagnosis, and especially in cases with serum values between 4-10 ng/ml, it must be combined with both rectal exploration and, above all, transrectal scan.