Reflux of bile and digestive enzymes from the small bowel and duodenum into stomach has been observed in patients with various gastroduodenal diseases. Tc-99m iminodiacetic acid delivatives hepatobiliary scan has been used as a noninvasive method to detect duodenogastric reflux. Sometimes, gastric reflux can be observed incidentally on routine Tc-99 DISA hepatobiliary scintigraphy. To evaluate the clinical meaning of gastric reflux on routine Tc-99m DISIDA hepatobiliary scan, we analyzed 36 patients showed gastric reflux incidentally on the routine Tc-99m-DISIDA hepatobiliary scintigraphy from December 1991 to June 1995 in Chungnam National University Hospital. The results were as follows: 1) The gastric reflux was observed in 2.3% of 1,553 cases of routine Tc-99m DISIDA Hepatobiliary scintigraphy for 43 months. 2) Nineteen percent of patients with gastric reflux had the past medical history of operations on stomach or biliary system. And that histoy was more prevalent in patients with reflux than those without reflux, significantly (p〈0.01). 3) On fiberoptic gastroduodenpscopic examination, 87% of the patients with gastric reflux had the gastroduodenal diseases such as gastritis, gastric ulcer, duodenal ulcer, gastric cancer, duodenal cancer and ampullary diverticulosis. We thought that the gastric reflux can be observed considerably in patients without any operation history on stomach or duodenum, although the operation history is more prevalent in patients with gastric reflux than those without reflux, significantly and most of patients with gastric reflux on routine Tc-99m DISIDA scan has various gastroduodenal diseases.