The significance of recent motor data on the distal colon in irritable bowel syndrome is obscured by methodological questions such as bowel preparation, variability and reproducibility of motor activity and segmental differences. Thirty subjects were studied after prior bowel cleansing with a water enema on two separate occasions 1 wk apart (10 with one bowel movement per day, 10 with two to three per week, and 10 with three to 12 per day). Two additional studies were performed in 10 of the subjects, one with and one without prior cleansing. The motility indices of the cleansed and unwashed colon were dissimilar. The motility index per 3 min varied markedly over 3 h, and the indices between the paired studies were rarely identical. Marked segmental differences were noted. The mean motility index per 3 min of the constipated and the diarrhea groups was significantly greater than that of normals only in the 15-cm segment. In view of these variables, caution should be exercised in the interpretation of basal motor activity of the distal colon.