Estimation of prostate gland volume with transrectal ultrasonography (TRUS) provides important information in the evaluation of benign and malignant prostate disease. We evaluated 119 patients with clinically benign prostatic hyperplasia (BPH) by TRUS. Sixty-eight of these underwent transurethral resection of the prostate (TUR-P), and 51 patients underwent open prostatectomy. In both groups the estimated weight correlated well with the removed prostatic weight (r = 0.643, p < 0.0001 in TUR-P and r = 0.729, p < 0.0001 in open prostatectomy). We found that TRUS is a valuable method for estimation of prostatic volume in patients with BPH.