PURPOSE:Constipation is a common problem in patients with spinal cord injury. The aim of this study is to analyze the role of pelvic floor dysfunction in the development of constipation.METHODS:Twenty‐five patients with clinically complete supraconal spinal cord injury were studied by means of colonic transit time, anal manometry, electrophysiologic testing, and sensory‐evoked potentials.RESULTS:Sixteen patients had prolonged total and segmental colonic transit times (Group C), and nine patients had normal colonic transit times (Group NC). Basal pressure and anal pressure during coughing, Valsalva's maneuver, and rectal distention were diminished in all patients, but no differences were observed between Group C and Group NC. Rectal sensation was preserved in eight patients, but this was not related to the absence of constipation. In seven of these eight patients, somatosensory‐evoked potentials could be recorded, which indicated an incomplete cord lesion. Synergic relaxation of the pelvic floor during straining was never observed; dyssynergia was seen in ten (7 in Group C and 3 in Group NC;P= not significant) patients. Associated peripheral nerve damage was present in 40 percent of patients but did not predispose these patients to constipation.CONCLUSIONS:Loss of rectal sensation, dyssynergic pelvic floor contraction during straining, associated peripheral nerve damage, and insufficient rise of intra‐abdominal pressure could not be held responsible for constipation as a result of spinal cord injury. A prolongation of the colonic transit time is the most important mechanism, and therapy should be directed toward it.