Transrectal ultrasonography (TRUS) was used to guide 277 biopsies of the prostate in 182 patients. The Bard Biopty system was used. Of these 182 patients, 107 (59%) had benign changes, and 75 (41%) had malignant lesions. Of those with cancer, 40% (30/75) had negative results of digital rectal examination (DRE). The cancer detection rate by TRUS was 40.7%, and by DRE alone it was 24.2%. Use of TRUS before transurethral resection of the prostate (TURP) in 47 patients with negative findings on DRE yielded 22 cancerous lesions (47%). We advocate this method in patients with abnormalities detected on DRE or with elevated levels of prostate-specific antigen or prostatic acid phosphatase, and as preoperative screening in patients having TURP because of the potential impact of a preoperative diagnosis of cancer upon the choice of treatment.