UNLABELLED: This study was designed to investigate the reproducibility of the results obtained from 99mTc-dimethyliminodiacetic acid (99mTc-EHIDA) cholescintigraphy, when used as a method of estimating gallbladder emptying. METHODS: In a random controlled fashion, the reproducibility of scintigraphic gallbladder emptying studies was assessed in 30 subjects, of whom six were normal, four had duodenal ulcers and the remaining 20 had undergone antiulcer gastric surgery. In fasting subjects, who 30 min later drank 250 ml of fresh milk, 2 mCi of 99mTc-EHIDA was intravenously injected. Liver and gallbladder areas were scanned for 60 sec and then every 5 min for 1 hr. The study was repeated in all subjects within 2-5 wk. From the gallbladder emptying curves, the duration of the lag phase (time from milk ingestion to actual start of emptying), the ejection fraction of emptying (peak to least activity in the gallbladder), the time by which maximal emptying was achieved and the pattern of gallbladder emptying were calculated. RESULTS: Two subjects were excluded from the study because their gallbladders did not fill. Lag phase duration was well reproduced in duplicate studies (r = 0.87), as was ejection fraction (r = 0.84). The time by which maximal emptying was achieved was not sufficiently reproduced. The normal pattern of emptying (exponential function) was reproduced in all controls, subjects with duodenal ulcers and patients after antiulcer surgery that did not involve duodenal exclusion. The abnormal pattern of emptying, characterized by refilling, was reproduced in five of the seven patients with gastric surgery that mainly involved duodenal exclusion. CONCLUSION: Scintigraphy with 99mTc-EHIDA to assess gallbladder motility is a method with satisfactory reproducibility of both parametric variables and patterns of emptying.