Since 1977, 184 patients with colitis or polyposis underwent colectomy with endorectal ileal pullthrough in two stages with a temporary ileostomy. Five had an S reservoir, three had a J reservoir, and 15 had no reservoir; 97 patients had a lateral reservoir constructed at the second operation and 64 had one constructed at the first operation. Ten patients with no reservoir and one with a J reservoir underwent conversion to a lateral reservoir because of stool frequency. Three patients with an S reservoir and six (3.5%) of 172 patients with a lateral reservoir underwent a permanent ileostomy. Over 65% of complications occurred in the first 50 patients. Late reservoir shortening was necessary in 34 patients. Of the last 110 patients, 107 are functioning well with a mean of six bowel movements per day. A short lateral reservoir (less than 15 cm) constructed at the first operation produces the fewest complications and best results.