BACKGROUND Abnormalities involving smooth muscle function in different systems of the body have been reported in irritable bowel syndrome (IBS). There are a few studies on gallbladder function in this disorder with conflicting results. OBJECTIVE To investigate the motility of gallbladder in patients with IBS. METHODS Forty-eight patients (15 male and 33 female) with IBS and 48 healthy volunteers (15 male and 33 female) were included into the study. Thirty-four patients (70.8%) had constipation predominant and 14 patients (29.2%) had diarrhoea predominant type of IBS. Fasting and postprandial gallbladder volumes were studied using real time ultrasonography and ejection fraction (EF) of gallbladder was calculated. RESULTS While fasting gallbladder volume (FGV) was similar between IBS and control groups (18.0 +/- 4.0 ml vs. 17.8 +/- 4.9 ml, p >0.05), postprandial gallbladder volume (PGV) was lower in IBS group than in the control group (5.5 +/- 1.4 ml vs. 6.2 +/- 1.9 ml, p = 0.03). Accordingly, the mean EF of gallbladders was found to be higher in IBS group than in the control group (69.1% vs. 64.1%, p = 0.0001). There were no difference in FGV, PGV and EF of gallbladders between constipation predominant and diarrhoea predominant IBS patients (p >0.05). CONCLUSIONS The results of this study indicated that IBS patients have increased emptying of gallbladder compared to healthy subjects.