Background/Aims: Experimental studies have shown gut hypersensitivity in irritable bowel syndrome. The aim of this study was to determine whether heightened perception of gut distention in irritable bowel syndrome is related to either decreased gut compliance, altered mechanosensitive afferents, or nonspecific sensory dysfunction. Methods: In 17 patients with irritable bowel syndrome and 15 healthy controls, stimulus-related perception of (1) intestinal balloon distentions, (2) transmucosal electrical nerve stimulation (15 Hz, 100 μs), and (3) somatic transcutaneous electrical nerve stimulation (100 Hz, 100 μs) was measured. Individual stimuli of 1-minute duration were randomly applied at 5-minute intervals. Results: Patients tolerated smaller intestinal volumes than controls (33 ± 3 mL vs. 43 ± 4 mL, respectively; mean ± SE; P < 0.05), whereas both intestinal compliance and perception of transmucosal electrical nerve stimulation were normal (patients tolerated 58 ± 5 mA and healthy subjects tolerated 69 ± 5 mA). Interestingly, patients perceived both stimuli more diffusely than controls; 48% ± 9% distentions and 52% ± 9% electrical stimuli were perceived over more than one abdominal region vs. 21% ± 9% and 18% ± 6%, respectively, in controls (P < 0.05 for both). In contrast to gut distentions, patients showed higher tolerance of somatic stimuli than controls (68 ± 7 mA vs. 42 ± 6 mA, respectively; P < 0.05). Conclusions: Patients with irritable bowel syndrome show selective hypersensitivity of intestinal mechanosensitive pathways associated with a nonspecific, probably central dysfunction of viscerosomatic referral. © 1995.