One hundred eleven patients who had undergone surgery for benign anorectal disease under spinal anesthesia were studied retrospectively to determine the incidence of postoperative urinary retention requiring catheterization and to assess possible influences on that incidence. The age group and sex of the patients did not affect the rate of retention. However, the use of a long-acting anesthetic agent and the administration of at least 1,000 mL of intravenous fluid perioperatively each produced a significant increase in postoperative urinary retention.