It has been suggested that enhanced esophageal peristalsis may be an additional reason for the therapeutic effect of oral bethanechol (B) in reflux patients and for the improved acid clearing seen with B. This study was designed to determine the effect of oral B on various parameters of esophageal peristalsis. Healthy young adult males were studied with an intraesophageal transducer assembly. Amplitude, dp/dt, and velocity profiles for the smooth muscle portion of the esophagus were produced. Oral B, 25 mg, produced a significant increase (P less than 0.05) in amplitude in the distal esophagus from 15 to 45 min after drug administration. The effect on dp/dt was similar but not as marked. Oral bethanechol produced decreases in velocity at all points, reaching significance (P less than 0.05) at the most distal measuring site, 30 and 45 min after injection. Oral B produces a stronger but slower, perhaps more efficient, progression of the peristaltic wave in normal humans. Our findings may explain improved acid clearance found with this agent.