The role of the vagus nerves in the control of postprandial motility in the upper gastrointestinal tract was investigated in four dogs by use of a bilateral cervical cooling blockade technique. On administration of food, the fasting migrating motor complex (MMC) was replaced by the postprandial (feeding) pattern. Feeding pattern duration varied in a dose-dependent manner with either total volume or calories of food. During the feeding pattern, oscillations in lower esophageal sphincter (LES) pressure occurred at time intervals equivalent to the MMC cycle period. Twenty-one control feeding experiments and 17 postprandial vagal blockade experiments were performed, with a minimum of three of each type in each dog. Vagal blockade, initiated at times ranging from 15 min to 4 h after feeding and maintained for up to 5 h, abolished the postprandial activity in the upper gastrointestinal tract. During postprandial vagal blockade, LES pressure was abolished and bursts of contractions were observed only in the upper small bowel, a pattern resembling that observed during vagal blockade in the fasted state. These bursts occurred at the expected times relative to, and their cycle period was not significantly different from, that of the MMCs recorded prior to feeding. Vagal blockade started prior to feeding prevented initiation of the fed pattern, which appeared immediately on termination of the blockade. We conclude that initiation and maintenance of the postprandial pattern in the upper gastrointestinal tract with concurrent inhibition of the fasting MMC normally require vagal integrity. The "clock" controlling the MMC cycle period is not reset by feeding, but its effect on motility is suppressed.