Acute urinary retention is a common complication following anorectal surgery. However, the cause of this complication is poorly understood. We investigated the influence on postoperative urinary retention of age, sex, premedicants, intraoperative fluid volume administered, surgeon, operating time, type of operation, anesthetic technique in 278 patients undergoing elective surgery for benign anorectal disease by a review of the charts. The results were as follows. The overall urinary retention rate was 31.7%. Age, sex, premedicants (narcotics, anticholinergics), surgeon did not correlate with urinary retention. Increasing age was associated with a relatively high incidence of urinary retention, but the difference did not reach statistical significance (P=0.054). The variables of intraoperative fluid volume administered (>200 ml), anesthetic technique (spinal anesthesia vs. general or caudal anesthesia), type (hemorrhoidectomy, especially including multiple mucosal ligation or sphincterotomy) of the operation, and operating time (>30 min) correlated significantly with retention (P<0.05). Urinary retention was 2, 7 and 3 times more likely to occur in patients who had duration of operation more than 30 minutes, hemorrhoidectomy, and spinal anesthesia respectively. After all above variables were controlled for, duration and type of the procedure and anesthetic technique remained significantly correlated with retention (P<0.05). We concluded that operating time of more than 30 minutes, hemorrhoidectomy (especially using multiple mucosal ligations or sphincterotomy), and spinal anesthesia were significant precipitating factors, but could not determine whether age and intraoperative fluid volume administered were associated with urinary retention with this retrospective study.