OBJECTIVE Minimal information exists on the characteristics and effect of esophageal shortening during peristalsis in the human esophagus. The aim of this study was to quantify esophageal shortening during peristalsis and determine the relationship between shortening, circular muscle contraction, and generation of propulsive force. METHODS Ten volunteers had three metal clips endoscopically affixed at the squamocolumnar junction and 4.5 and 9 cm proximal to it, defining proximal and distal segments in the lower esophagus. A strain gauge manometer was positioned within the proximal segment along with a traction force sensing balloon. Axial clip movement was assessed with concurrent manometry and videofluoroscopy during swallowing to examine the determinants of propulsive force. RESULTS Esophageal shortening was coordinated with circular muscle contraction such that each propagated distally as overlapping segments of contraction at a velocity of about 2.5 cm/s. Propulsive force within the proximal segment occurred after shortening, during the circular muscle contraction, with the magnitude of propulsive force correlated with the degree of distal shortening. CONCLUSIONS (1) Both circular and longitudinal esophageal muscle contraction occur as propagating segments during peristalsis, with the longitudinal muscle contraction leading the circular muscle. (2) Propulsive force occurs during proximal circular and distal longitudinal muscle contraction.