OBJECTIVE To assess gallbladder (GB) volume variations in response to a standard meal. METHODS We assessed these variations with ultrasonography at brief intervals over the postprandial period, which included the emptying and refilling phases of the GB. RESULTS During both emptying and refilling of the GB, the volume fluctuated continuously, with brief alternating volume decrements and increments. The phases of emptying and refilling appear to be the net result of the algebraic sum of these volume fluctuations. In the emptying phase, the volume decrements showed a greater volume (35.7 +/- 10.7 ml vs. 14.8 +/- 8.4 ml) and lasted longer (158 +/- 37 min vs. 85 +/- 44 min) than the volume increments, whereas the opposite took place in the refilling phase (4.3 +/- 3.4 ml vs. 16.4 +/- 12.2 ml; 39 +/- 20 min vs. 84 +/- 37 min). CONCLUSIONS It is probable that the continuous GB volume fluctuations are the expression of hepatic bile recycling in the GB during the entire postprandial period, and the amount of bile recycled by the GB is greater during the emptying than the refilling phase.