BACKGROUND/AIMS: A contentious issue in medicine is whether or not patients with irritable bowel syndrome (IBS) have abnormal motor physiology, and also whether the sensory and motor physiologies are different between the patients suffering with the various subtypes of IBS. Our aim was to investigate if IBS patients have different sigmoid accommodation compared with the normal controls or if the differences exist in sigmoid accommodation according to the IBS subtype. METHODS: Fifteen Rome II positive IBS patients and 7 normal controls were recruited for the study. A sigmoid bag catheter was endoscopically placed, and then bag inflation was performed via a barostat. Sigmoid accommodation was measured by using the rapid phasic distention method. RESULTS: In the IBS patients, sigmoid accommodation (1.0 ml/s) was significantly lower than that of the controls (1.3 ml/s). There were no statistically significant differences in sigmoid accommodation according to the IBS subtype, but the IBS patients with predominate symptoms of diarrhea had a tendency for lower sigmoid accommodation (p=0.051). Gastrointestinal symptoms and stool frequency did not seem to have any correlation with sigmoid accommodation. However, for the IBS patients with predominate symptoms of constipation, the stool frequency tended to be associated with the sigmoid accommodation (p=0.052). CONCLUSIONS: Sigmoid accommodation was significantly lower in the IBS patients. The results are generally consistent with the finding that the IBS patients with predominate symptoms of diarrhea exhibit a tendency for lower sigmoid accommodation.