Five patients with urcerative colitis and familial adenomatous polyposis were manometrically studied and compared with 8 healthy volunteers (5 males and 3 females, aged 12-18 years with a mean age of 15.6 years) as controls. The patients underwent total colectomy, mucosal protectomy, and ileal J pouch-anal anastomosis (2cm of muscular rectal cuff). There were 3 males and 2 females, aged 10-15 years with a mean age of 13.0 years. Four patients (80%) one year after the closure of the diverting ileostomy had experienced a small amount of soiling and had significantly lower anal resting and squeezing pressure as compared with patients two years after the closure of diverting ileostomy and normal subjects (p<0.05). The results suggested that anorectal dysfunction in one year after operation is due to injury to the anal canal sphincter caused during the operation. The damage to the anal sphincter was improved two years after the closure of the diverting ileostomy.