Myoelectric spike bursts were recorded in the sigmoid colon by means of an intraluminal silastic tube equipped with 3 Ag−AgCl ring electrodes fixed 15 cm apart on the tube that was introduced by flexible sigmoidoscopy. In six subjects, the tube was also equipped with three catheters whose tip opened 1 cm aborad from each electrode, for pressure recordings. In six other subjects, the tube was equipped with both electrodes and a catheter opening at the tip of the probe for infusing fluids at a rate of 12 ml/min into the colonic lumen. The fluid was collected with another tube inserted in the rectum and the volume was measured at 1-min intervals. Colonic spiking activity was made of rhythmic stationary bursts (RSB) and of sporadic bursts that were either propagating (SPB) or not propagating (SNPB). All sporadic bursts were associated with intraluminal pressure waves whose amplitude was significantly higher than that associated with rhythmic bursts. In the infusion experiments, the volume of fluid collected did not change significantly whether rhythmic bursts were present or not (3.9±1.7 ml/min and 3.3±1.9 ml/min respectively) (mean±sd). However, the volume was significantly higher when sporadic nonpropagating bursts were present (9.4±4.1 ml/min), and even higher when the sporadic bursts were propagating (21.6±8.8 ml/min). These results indicate that (1) the occurrence of sporadic bursts, particularly when propagating, is associated with intraluminal pressure waves that lead to significant propulsive movements; and (2) rhythmic bursts do not seem to be involved in colonic propulsive activity.