Background/Aims: We have previously shown that patients with functional dyspepsia are hypersensitive to gastric distention. The aim of this study was to establish whether this sensory disturbance was confined to the stomach and whether it was associated with gut reflex dysfunction. Methods: In 10 selected patients with dyspepsia and 12 healthy controls, perception and gut reflex responses to gastric distention, duodenal distention, and somatic stimulation were measured. Standardized distentions at fixed pressures were performed by gastric and duodenal barostats. Perception was scored by a detailed symptom questionnaire; gut reflex responses were measured as isobaric volume changes by each barostat. Somatic transcutaneous electrical nerve stimulation was produced on the hand. Individual stimuli (2-minute duration) were randomly applied at 10-minute intervals in stepwise increments in search of the respective threshold for discomfort. Results: Patients with dyspepsia had gastric hypersensitivity to distention (discomfort threshold at 6.4 ± 0.4 mm Hg vs. 8.3 ± 0.6 mm Hg in controls; mean ± SE; P < 0.05), whereas duodenal and somatic sensitivity was normal. Furthermore, patients with dyspepsia explicitly recognized their clinical symptoms in all gastric but only in 58% ± 12% of the duodenal distention trials. In addition, patients with dyspepsia showed defective gastric relaxatory responses to duodenal distention (68 ± 30 ml gastric expansion vs. 239 ± 12 mL in controls; P < 0.05). Conclusions: Patients with dyspepsia are selectively hypersensitive to gastric distention; this sensory dysfunction is associated with impaired reflex reactivity of the stomach. © 1994.