Anorectal function was measured in 11 patients with active medically intractable ulcerative colitis, seven patients with quiescent ulcerative colitis, and 18 healthy subjects. The anal resting pressure, squeeze pressure, and ability to defecate a balloon were similar in all groups. Significantly lower rectal distention volumes were required for rectal sensation, critical volume, and to induce rectal contractility in patients with active disease compared to controls or patients with quiescent disease. Rectal compliance was significantly reduced in patients with active and quiescent disease. The increased rectal sensitivity and contractility in patients with active colitis appear to be related to active mucosal inflammation and ulceration. Episodes of mucosal inflammation may be responsible for chronic changes in the rectal wall resulting in fibrosis and decreased compliance in patients with quiescent disease. The frequency and urgency of defecation and the fecal incontinence may be due to a hypersensitive, hyperactive, and poorly compliant rectum.