Lower esophageal sphincter (LES) pressure, as well as esophageal peristaltic amplitude, duration, and velocity were measured in 16 infants with gastroesophageal reflux before administration of subcutaneous bethanechol, and at 10, 20, and 30 min after. Seven infants received 0.1 mg/kg, and 9 received 0.2 mg/kg. Significant increases in LES pressure occurred at both doses and lasted for 20 min. The amplitude and duration of peristaltic contractions were increased only after the larger bethanechol dose, and the increases were of greater magnitude in the distal esophagus than in the middle esophagus. The velocity of peristalsis decreased significantly in both the lower and middle esophagus, but only after the larger dose of bethanechol. Bethanechol had no effect on any motor function of the upper third of the esophagus. The changes in esophageal peristalsis produced by bethanechol may improve the efficiency of distal esophageal acid clearance and thus may be responsible in part for the therapeutic effect of bethanechol in infants with gastroesophageal reflux.