Bile reflux has been implicated in the pathogenesis of gastritis, gastric ulcer, and esophagitis. Radionuclide techniques provide the only non-invasive method to detect duodenogastric reflux. To analyze the problems that occur with attempts at quantitation, 55 patients were prospectively evaluated (45 patients with reflux esophagitis or Barrett's esophagus and ten patients with clinical symptoms of bile reflux, four of whom had Bilroth II surgery) with Tc-99m DISIDA, using a fasting technique with gallbladder stimulation by sincalide. Visual duodenogastric reflux occurred in 16 of 55 patients. Overlap of small bowel with the stomach is the major problem for accurate quantitation and occurred in 20 of 55 patients (36%). Overlap of left lobe of the liver occurred in 40 of 55 patients (73%), but its contribution to gastric activity was slight and could be easily subtracted. Reflux was intermittent in six of the 16 positive studies (38%), and continuous computer acquisition is needed to detect its maximum value. Primarily because of the problem of small bowel overlap, scintigraphic evaluation of duodenogastric reflux is only, at best, semi-quantitative. A review of the technical variables used in this examination, as well as potential problems that can occur, is provided.