Aim: Biliary dyskinesia ( BD) is characterized by symptoms of biliary disease, no evidence of gallstones on ultrasonography (USG), and diminished gallbladder ejection fraction. The diagnosis is based on findings of abnormal gallbladder ejection fraction diagnosed by hepatobiliary scintigraphy before and after stimulation of gallbladder contraction with cholecystokinin (CCK). We used an easier diagnostic technique defined as ultrasonographic evaluation of fatty meal stimulated gallbladder contraction, employing USG with the diagnosis of biliary dyskinesia in children. The study was conducted by USG to investigate the volume and contractility of the gallbladder (GB) in fasting conditions and 45 min after a standardized fatty meal (SFM) in normal children and in a group of BD patients, and to compare the diagnostic value of this test with scintigraphy and to evaluate its use as a new method in the diagnostic algorithm of BD. Methods: We assessed the volume changes and contractility of the GB in response to SFM by USG in 14 patients with BD diagnosed by cholecystokinin stimulated hepatobiliary scintigraphy (CCKs-HBS); and compared them with 14 control patients matched for age and gender before cholecystectomy. After an overnight fasting, GB volume was measured by USG then the GB volume was again measured after the SFM ingestion. Using USG, length, width and height of GB were measured, and volume of the GB was calculated using the 'Dodds' formula. These volume measurements were used to calculate the percentage of gallbladder emptying (ejection fraction). Fasting, after SFM and EF values comparisons between groups were done with student's t-test. Results: No statistically significant difference of fasting GB volumes were demonstrated between BD and control groups (14.19 +/- 6.7 cm(3) and 13.49 +/- 4.0 cm(3) respectively). GB volumes of the BD group after SFM were significantly greater than in healthy controls (13.19 +/- 1.8 cm(3) and 3.49 +/- 0.9 cm(3) respectively, P < 0.0005). The calculated percentage of gallbladder contraction (ejection fraction) was found to be lower in BD patients than in healthy controls (7.1% +/- 1.8% and 73.8% +/- 6.4%, respectively, P < 0.0005).