In evaluating gallbladder function, the clinical feasibility of three-dimensional (3-D) ultrasound (US) using volumetric acquisition was assessed in 30 patients: 18 patients with gallstones and 12 healthy volunteers. 3-D ultrasonography was performed in each patient before and after a fat-meal test. The ejection fraction of the gallbladder from two volumes measured by computer-aided analysis was calculated. There were significant differences in the gallbladder ejection fractions among the diseased and control groups (p < 0.0001). Compared with the results of oral cholecystograms, the ejection fraction of the gallbladder using 3-D volumetry and the grade of oral cholecystography showed good correlation in predicting the gallbladder dysfunction (gamma = 0.71, p = 0.002). Even in cases failing oral cholecystography, the gallbladder ejection fraction using 3-D US was calculated without any difficulty. Conclusively, volumetric acquisition of 3-D US enables us to evaluate gallbladder function and provides a reliable diagnostic yield superior to oral cholecystography.