Previous manometric studies of the ileocolonic junction were performed without assessing the precise spatial relationship between recording sensors and ileocolonic junction. In the present study, the motor activity of the ileocolonic junction was recorded using manometric sensors localized under direct colonoscopic control in 11 patients (4 men, 7 women; mean age, 55 years) referred for hematochezia with normal stool frequency. No medications were administered before and during endoscopy. A perfused catheter (OD 1.7 mm, with three side holes 4 mm apart and marked by evenly spaced black rings in the distal 6 cm) was passed through the biopsy channel of the endoscope and advanced through the ileocolonic junction and 6 cm into the ileum. The catheter was then withdrawn into the cecum by 1-cm steps, and motor activity was recorded for 4-6 minutes at each station. A single catheter taped to the endoscope continuously recorded cecal pressure. An ileocecal pressure gradient could not be identified in the majority of subjects; individual values ranged from -8 to +4 mm Hg, and gradients were maintained over the entire length of the ileum. In the distal ileum, tonic and phasic pressure waves were detected. Tonic variations were present for 70.1% of the recording time, either alone (44%) or together with phasic waves (56%). Phasic waves were present for 10.3% of the recording time and, according to their duration, were subdivided into those compatible with the rate of ileal slow waves and prolonged waves not compatible with the rate of ileal slow waves. Regular phasic waves could be either isolated or in clusters; prolonged waves were always isolated. A similar proportion of regular (27.9%) and prolonged (31.2%) phasic waves propagated aborally along the ileum or from ileum to cecum. Clusters presented an average of 8.7 +/- 0.6 peaks/min, and 44% of them propagated aborally. The manometric characteristics did not vary between the segments 5-3 cm and 2-0 cm proximal to the ileocecal junction. In conclusion, a powerful ileocecal sphincter was not detected at the human ileocecal junction, and motor activity of the distal ileum was characterized by tonic changes and rapid phasic contractions.