Concurrent videofluoroscopy and manometry were used to analyze esophageal emptying during barium swallows in 22 patients with axial hiatal hernias and in 14 volunteers. Subjects were divided into three groups: (a) volunteers with maximal phrenic ampullary length less than 2 cm (controls); (b) patients or volunteers with maximal ampullary/hiatal hernia length greater than or equal to 2 cm that reduced between swallows (reducing-hernia group); and (c) patients with hernias that did not reduce between swallows. Complete esophageal emptying without retrograde flow was achieved in 86% of test swallows in the controls, 66% in the reducing-hernia group, and 32% in the nonreducing-hernia group (P less than 0.05). Impaired emptying in the reducing-hernia group was attributable to "late retrograde flow," whereby barium squirted retrograde from the hernia during emptying. Impaired emptying in the nonreducing-hernia group was attributable to "early retrograde flow" that occurred immediately after LES relaxation. The nonreducing-hernia group also had longer acid clearance times than the controls (P less than 0.05). We conclude that gastroesophageal junction competence is severely impaired in patients with nonreducing hiatal hernias, suggesting a mechanism whereby this subgroup of hiatal hernia is involved in the pathogenesis of reflux disease.