Conventional radiographic and manometric criteria failed to distinguish 9 irritable bowel syndrome patients with the symptom of rectal dissatisfaction from 6 without it. Manometric values (including sphincter length, resting and squeeze pressures, and the rectoanal inhibitory reflex, as well as rectal compliance and maximum tolerable volume), radiographic indices (anorectal angle and level of pelvic floor at rest and on straining), and tests of anal and rectal sensitivity were all statistically indistinguishable. Conceivably, the symptom results from incomplete rectal emptying; it may also be an early warning of abnormal perineal descent. Only 4 of the 15 patients with irritable bowel syndrome in this study were able to expel a 50-ml balloon from the rectum in the left lateral position.