We assessed the effect of previous abdominal colectomy on functional results after ileal "J" pouch-anal anastomosis (IPAA) in patients with ulcerative colitis. Twenty-five patients with colectomy prior to IPAA were compared with 22 patients who underwent noncolonic abdominal operations prior to IPAA. No differences were observed in pre- or postoperative resting anal sphincter pressure, squeeze pressure, or rectal inhibitory reflex. Previous colectomy was associated with a greater incidence of postoperative small bowel obstruction. Mean ± SEM daily stool frequency at 1 and 12 months postoperatively, respectively, was 8.9±0.8 and 5.7±0.3 for patients who had undergone previous colectomy, and 8.2±0.7 and 6.0±0.5 for the no previous colectomy group (p=not significant). At the same postoperative intervals, nocturnal stool frequency was 1.9±0.3 and 1.1±0.2 for the colectomy group and 1.5±0.3 and 0.6±0.1 for the no colectomy group (p=0.05 at 1 year). More patients in the previous colectomy group had greater than or equal to 1 nocturnal stool after 1 year (71% versus 33%, p=0.03). Although pouch capacity at 1 year was not different in the 2 groups, pouch capacity was directly related to stool frequency in the no colectomy group (r2=0.48, p=0.01), but not in the previous colectomy group (r2= 0.08, p=not significant). We conclude that previous abdominal colectomy may be associated with a higher overall incidence of small bowel obstruction. Moreover, previous colectomy is a determinant of postoperative nocturnal stool frequency after IPAA, most likely due to altered ileal pouch function. When possible, single-stage colectomy, mucosal proctectomy, and endorectal ileal pouch-anal anastomosis should be performed in patients requiring colectomy for ulcerative colitis. © 1990 Société Internationale de Chirurgie.