Sensory and pressure responses to gastric distension were evaluated in 24 consecutive patients suffering from chronic idiopathic dyspepsia and 20 healthy subjects. A latex balloon was placed in the proximal stomach and inflated by increments of 100 ml of air up to a maximal volume of 800 ml. Symptom response and intragastric pressure-volume curve were recorded during the gradual balloon distension. Thirteen of the 24 patients experienced pain at a distension volume less than or equal to 400 ml of air, but only one of the 20 controls (P less than 0.001). Intragastric pressure-volume curves were similar in patients and controls, and in patients with and without abnormal pain threshold, suggesting that a compliance defect was not the cause of the sensory anomaly. Gastric emptying of solids and liquids was measured in 20 of the 24 patients using a dual isotopic technique; psychological status was also evaluated in 18 patients using the Mini-Mult test. The frequency of the sensory anomaly was not different in patients with (7/14) or without (4/6) gastric stasis, but was lower in patients with (5/13) than in those without psychological disturbances (5/5, P less than 0.01). Thus, a primary visceral sensory anomaly, either alone or in conjunction with motility disturbances, can play an important role in chronic idiopathic dyspepsia and must be taken in account for further therapeutic research.