Tc-99m IDA compounds have been used in the quantitative analysis of motor function of the gallbladder. However, stimuli to provoke emptying have been variable and frequently nonphysiologic. To determine the utility and dependability of provocative agents for gallbladder emptying, we studied the effects of Lipomul, CCK, and TRH after the intravenous administration of Tc-99m disofenin. Computer processing of region-of-interest over the gallbladder permitted time/activity analysis of each study and computation of the ejection fraction (EF). Results showed that Lipomul consistently produced an effect on gallbladder emptying (EF 16-42%). CCK, while more dramatic in response, was less predictable (EF 8-100%). TRH favored accumulation of activity and did not cause gallbladder emptying. The combination of CCK and TRH decreased the rate of gallbladder emptying produced by CCK alone. We conclude that the availability, low cost, and dependable effect on gallbladder emptying make Lipomul the gallbladder stimulant of choice for clinical use.