Gastric electrical control activity (ECA) controls the sequence of occurrence of contractions in the gastric wall. Normally, the direction of phase lag among control waves is aborad, and hence a ring of contraction originates in the corpus and moves distally. This study was undertaken to determine if a reversal in the direction of phase lag among control waves by an electronic pacemaker surgically implanted near the pylorus in dogs would reverse the sequence of contractions and hence delay gastric emptying. Electrical stimulation was applied at 5.8 to 6.0 pulses per min, 50 to 80-msec pulse width, and 10 to 14-v pulse amplitude. Liquid gastric emptying was measured by introducing 400 to 600 ml of phenol red or phenol red plus barium sulfate by a nasogastric tube through an esophagostomy into the stomach and withdrawing the remainder after 5- and 15-min periods. Solid emptying was measured by means of radiological image intensifier observation of the gastric emptying of small barium-filled balls. The study shows that an electronic pacemaker implanted in the antrum reverses the normal aborad direction of movement of contractions and delays the gastric emptying of both liquid and solid meals.