Gallbladder emptying induced by a fatty meal (2 egg yolks) was studied by oral cholecystography in 402 subjects without gastrointestinal disorders. Roentgenograms were made at intervals up to the 6oth minute after the meal, and the radiopaque areas were measured planimetrically to provide a quantitative assessment of emptying. The pattern of emptying was compatible with an exponential function. The mean value for t½ was higher in the women; emptying tended to be slower in younger subjects.