Transurethral resection of the prostate is the most common surgical treatment for benign prostatic hyperplasia. We conducted a prospective randomized clinical trial to compare this surgery with medical treatment in men with moderate symptoms of benign prostatic hyperplasia. Of 98 men over the age of 54 years who were screened between June 1993 and June 1995, 53 were studied (25 in the surgery group and 28 in the medication group). Patients' symptoms and the degree to which they were bothered by urinary difficulties were measured with standardized questionnaires and medical evaluations. The men randomly assigned to the surgery group underwent surgery within 2 weeks after the assignment. Surgery was not associated with an impotence or urinary incontinence. The follow-up period was 1 year. Surgery was significantly associated with improvement in residual urinary volume and peak flow rate; and also in the scores for urinary difficulties, sexual performance and interference with activities of daily living (P < 0.001 for all comparisons). We concluded that for patients with moderate symptoms of benign prostatic hyperplasia, surgery is more effective than medication in improving genitourinary symptoms and enhancing the quality of life. Thus, medication as treatment should be reserved for patients who are less bothered by urinary difficulty or who wish to delay surgery.