Gastrocolic fistula formation is an extremely rare complication of gastric ulcer disease. We report a case of a 55-year-old man who presented with a two-month history of abdominal discomfort, postprandial diarrhea, nausea and faecal vomiting. Upper gastrointestinal endoscopy showed an ulcer in the greater curvature of the stomach. Barium enema examination revealed an obvious gastrocolic fistula between the greater curvature of the stomach and the transverse colon. The involved segment of the colon was excised and truncal vagotomy and antrectomy was performed. The patient was discharged on the 711 postoperative day. It is concluded that cases with postprandial diarrhea and nutritional disturbances after gastric surgery should remind us of the probability of gastrocolic fistula formation.