The normal pattern of resting and post-prandial motor activity in the gastric antrum has been established by observations in 6 dogs. There was a gradual increase in the amplitude of contraction during the first 2 hours after eating; this was maintained for 3 hours and then declined. For the first 45 minutes terminal antral contraction occurred, partially retaining and triturating the gastric contents. After 45 minutes the waves became sequential, symmetrical, increased in vigour and actively pumped food into the duodenum. Vagotomy modified the mechanism of the antrum in various ways. Truncal and selective vagotomy reduced the work capability to 20 per cent of its normal value when recorded 1 month after operation. In both groups the waves were disorganized. Proximal gastric vagotomy abolished the braking mechanism and removed the initial inhibitory stimuli to antral motility. Within 1 month of operation the antrum had regained 58 per cent of its normal work capability and the contractions were well organized.