Complications of extended gastric surgery and their prevention were discussed. To determine the incidence of postoperative complications, 1,114 gastric cancer patients with radical lymph node dissection (D2 or more) were examined. The postoperative complication rate following total gastrectomy (30.9%) was significantly higher than that following distal gastrectomy (14.6%). In total gastrectomy cases, the rate of postoperative complications in D4 dissection cases (50.0%) was significantly higher than in D2 (29.8%) and D3 (22.4%) dissection cases. Moreover, the more extensive the combined resection, the greater the incidence of postoperative complications, anastomotic insufficiency and operative mortality. Concerning the complications accompanying lymph node dissection, hepatic dysfunction due to damage of the proper hepatic artery (2 cases), bile leakage (7 cases) and jaundice (1 case) due to damage to the biliary tract were seen. Ascites due to lymphorrhea following extended lymphadenectomy was recognized in 9 cases. The greatest cause of death was major leakage, the second was septicemia, the third was pneumonia and the fourth was intra-abdominal bleeding. For the prevention of these complications, in addition to meticulous attention to the pre-/postoperative management, careful operative manipulation to avoid damage to main abdominal blood vessels, lymph leakage, anastomotic leakage and pancreatic fistula is necessary.