The aim of this work was to answer the two following questions: 1) is there any difference between the right colonic, the left colonic, and the rectosigmoid motility? 2) does the rectosigmoid junction (radiological and endoscopic entity) exhibit a specific motility pattern? Colonic motility was assessed by electromyography. We used an intraluminal probe supporting 15 groups of 3 ring electrodes. Inside the probe a lead pellet was placed opposite each electrode. The probe was inserted through the colon by colonoscopy. A visual analysis of the signal was performed and we distinguished: Long Spike Bursts (LSB) activity (propagating in oral or aboral direction or not propagating) from Short Spike Bursts (SSB) activity as previously described. Twenty patients suffering from the irritable bowel syndrome included in a subgroup defined as abdominal pain, were studied, and two groups were defined as follows: the tip of the probe was positioned in the caecum in 9: group "Right colon" patients. An electrode was specifically located on the rectosigmoid junction in 15: group "Junction" patients. In the "Right colon" group, the postprandial increase of LSB activity in the rectosigmoid lasted longer than in the right and left colons. During the postprandial period, the right colon exhibited a lower LSB activity than the rectosigmoid (p less than 0.01). After the meal LSB activity propagating in aboral direction was increased in the right colon while it was inhibited in the rectosigmoid. LSB activity propagating in the oral direction was increased both in the right colon and rectosigmoid after the meal. In the "Junction" group, we observed a specific myoelectrical activity at the rectosigmoid junction.(ABSTRACT TRUNCATED AT 250 WORDS)