A new noninvasive technique for the measurement of the gallbladder evacuation quantitatively is described. By using a radioactive bile marker [99mTc]HIDA, the evacuation of the gallbladder is measured nongeometrically in terms of ejection fraction (fractional bile volume emptied from the gallbladder) and ejection rate (dv/dt). The counts and volume in an in vitro gallbladder phantom under pinhole collimator geometry show a linear relationship (r = 0.998) enabling the replacement of gallbladder bile volume by bile counts before and after evacuation. The counts ejection-fraction shows a high degree of correlation (r = 0.998) with the measured-volume method. The movement of the gallbladder during respiration does not effect the measurement of ejection fraction. The technique allows simultaneous imaging and quantitation, and it is highly reproducible, carrying an interobserver and reproducibility mean error of 5%. This technique is suitable for studying the motor functions of the gallbladder and the effects of various pharmacologic agents on its evacuation. The clinical usefulness of the technique requires further testing.