The purpose of this single blind study was to verify the efficiency of Doxazosin Mesylate, an alpha-1 adrenergic blocker, in patients with benign prostatic hyperplasia (BPH). This study involved 20 patients non placebo responders. The duration of treatment was 45 days with administration of Doxazosin Mesylate increased every 15 days from 1 to 2 mg and from 2 to 4 mg respectively. At the end of each dosage cycle the following investigations were performed: a) peak urinary flow, b) residual urinary volume, c) funneling of the prostatic urethra by means of permictional transrectal echography, d) Boyarsky's score. The analysis of these data, applying a two way analysis of variance (ANOVA), showed that Doxazosin Mesylate resulted in improvements in both urodynamic and symptomatic parameters. The statistical analysis proved also that there was a good correlation between the dosage of the drug up until 2 mg and the results from each parameter considered.