This investigation determined the site(s) of elicitation and origin of secondary peristalsis in the human esophagus and characterized the upper esophageal sphincter (UES) and proximal esophageal body responses accompanying intraluminal distention. In 7 normal persons, an intraluminal transducer probe manometrically recorded the UES and 5- and 10-cm levels of the esophageal body. A second probe with a balloon attached 2 cm above the proximal strain gauge was located so that the balloon was 3 and 4 cm below the UES and 4 distentions were done. The balloon probe was moved in 2-cm increments (four distensions at each site) until lower esophageal sphincter pressures were recorded. No secondary peristalsis occurred after distention in the proximal 6 cm. The incidence of secondary peristalsis increased as the distention site moved distally. Sixty-nine per cent of secondary peristaltic waves orignated in the esophageal body proximal to the distention site. The UES pressure significantly increased over resting pressure (augmentation) during 63% of distentions. The esophagus proximal to the balloon and below the UES usually responded to distention with augmentation. Augmentation of the UES and proximal esophageal body in response to esophageal intraluminal distention and the resultant initiation of secondary peristalsis above the distention site comprise a highly integrated pressure barrier to esophagopharyngeal reflex.