Improvement of functional outcome after proctocolectomy for ulcerative colitis and familial adenomatous polyposis was compared between transanal ileal pouch-anal anastomosis (T-IAA group, n = 29) and double-stapled ileal pouch-anal anastomosis (DS-IAA group, n = 8). Clinical functions were evaluated using a functional scoring system, and physiologic functions by anorectal manometry after one year postoperatively. Although in the T-IAA group 4 of the 29 patients (13.8%) displayed partial incontinence (< 9 points), all of 8 patients in the DS-IAA group showed good results referring to continence (> 10 points). The maximum resting pressure was 44.3 +/- 5.2 cmH2O in the T-IAA group vs. 56.6 +/- 5.8 cmH2O in the DS-IAA group, and postoperatively the maximum squeezing pressure was 96.8 +/- 9.2 cmH2O in the T-IAA group vs. 106.3 +/- 8.1 cmH2O in the DS-IAA group. There was a significant difference of maximum resting pressure and no significant difference of maximum squeezing pressure between the two groups. The length of the high pressure zone in the anal canal was significantly shorter in patients of the T-IAA group (2.1 +/- 0.8 cm) than in those of the DS-IAA group (3.5 +/- 1.1 cm) (p < 0.05). The DS-IAA is associated with excellent objective physiologic and subjective functional results. This reflects the sacrifice of the internal anal sphincter 1.5 cm cephalad necessary to effect this anastomosis at a mean of 1.4 cm from the dentate line.