A 79-year-old woman with pneumobilia and liver dysfunction was admitted to our hospital. ERCP and gastrointestinal endoscopy revealed choledochal stones and a cholecystogastric fistula at the greater curvature of the gastric antrum. The risk of cholecystectomy and fistulectomy appeared to be extremely high for this patient because of her advanced age and low respiratory function due to interstitial pneumonia. Therefore, only an endoscopic lithotomy was performed, and the cholecystogastric fistula remained. However, after 2 years of follow-up, she developed an advanced gallbladder carcinoma. This finding suggests that cholecystogastric fistula is a risk factor for gallbladder carcinoma. Because of the difficulty of early detection of gallbladder carcinoma associated with cholecystogastric fistula, both fistulectomy and cholecystectomy are necessary when cholecystogastric fistula is diagnosed.