To evaluate the gastroesophageal (GE) scintiscan, a technique which detects and quantitates GE reflux, 30 patients with heartburn and a positive acid-reflux test and 20 normal control subjects were studied. Conventional diagnostic tests including barium esophagography, fluoroscopy, esophagogastroscopy, esophageal biopsy, acid perfusion testing, and esophageal manometry were performed on each patient with GE reflux. None of these techniques was sufficiently sensitive in detecting GE reflux. In contrast, GE reflux was visualized by scintiscanning in 27 out of 30 (90%) of patients. The GE reflux index was significantly greater in reflux patients, 11.7 +/- 1.8%, compared to controls 2.7 +/- 0.3%. These studies suggest that GE scintiscanning can detect GE reflux accurately, rapidly, noninvasively, and with greater sensitivity than other diagnostic techniques. In addition, it can be employed to quantitate GE reflux.