OBJECTIVE Colonic pouches have gained increasing popularity in reconstruction after low anterior resection. In this prospective, randomized trial colonic pouch reconstruction is compared with side-to-end anastomosis for functional outcome. METHODS From October 1995 to October 1996, 29 patients had colonic pouch and 30 patients had side-to-end anastomosis reconstruction after low anterior resection. Patients were matched for age, gender, and tumor stage and localization. All patients underwent functional evaluation preoperatively and at three and six months postoperatively. RESULTS There was no difference in preoperative anorectal function. The operating time was higher in the colonic pouch group (167 vs. 149 minutes). Twenty-three patients (79.3 percent) with colonic pouch had a protective stoma compared with 21 patients (70 percent) with side-to-end anastomosis. Postoperative complications were 10.3 and 13.3 percent, respectively. There was no difference in manometric pressure of the anus, in anorectal angle, and in continence status after three and six months. Stool frequency was higher in the side-to-end anastomosis group, with 2.2 vs. 5.4 per day at three months and 2.3 vs. 3.1 per day at six months. Constipation was noted in two patients with colonic pouch (7 percent) and none in the side-to-end anastomosis group at three months and two vs. none at six months. Maximum tolerated volume and threshold volume was higher in the colonic pouch group at three and at six months. CONCLUSIONS Both forms of reconstruction have similar satisfactory long-term functional results. The major advantage of colonic pouch was seen in the immediate postoperative phase.