To determine the relationship between perception of segmental intestinal distension and the reflex gastric tone response, we performed in eight healthy volunteers graded isobaric distensions (2.5 min duration at 10 min intervals) of the duodenum and the jejunum using an electronic barostat. We measured gastric tone as intragastric air volume by a separate barostat and the perception score by a graded questionnaire. At the threshold distending pressure for discomfort in the duodenum (23 +/- 2 mmHg), both perception (5.7 +/- 0.2 score; P less than 0.01) and reflex gastric relaxation (148 +/- 35 ml delta gastric vol; P less than 0.01) were elicited. Lower pressures (12 mmHg below the discomfort threshold) failed to produce perception (0.6 +/- 0.4 score), but significant relaxation was still induced (63 +/- 22 ml delta gastric vol; P less than 0.05). In contrast, no significant gastric relaxation occurred at any pressure level tested in the jejunum (up to 27 +/- 2 mmHg), whereas the perception scores paralleled those produced by duodenal distension. This dissociation between symptoms and visceral reflexes suggests that both responses are independently induced by specific mechanisms.