Our hypothesis was that rumination syndrome is associated with gastric sensory and motor dysfunction. We studied gastric and somatic sensitivity, reflex relaxation of the lower esophageal sphincter (LES), and gastric compliance and accommodation postprandially and postglucagon. A barostatically controlled gastric bag and esophageal manometry were used to compare gastric sensorimotor functions and LES relaxation to gastric distension in 12 patients with rumination syndrome and 12 controls. During bag distensions, patients had greater nausea, bloating, and aggregate score, but not pain, compared with controls (P < 0.05). At 4 and 8 mmHg gastric distension, LES tone reduction was greater in patients than in controls (P < 0.05). Gastric compliance, accommodation to a standard meal, and response to glucagon were not different in patients and controls; however, 6 of 12 patients had no gastric accommodation; the latter patients had significantly greater pain perception during distension (P < 0.05) but normal somatic sensitivity compared with healthy controls. Rumination syndrome is characterized by higher gastric sensitivity and LES relaxation during gastric distension. A subgroup of patients also had absent postprandial accommodation.