This randomized Phase II trial is being conducted to evaluate the impact of omentectomy for advanced gastric cancer on patient survival. The primary endpoint is the 3-year relapse-free survival rate and the secondary endpoints are 5-year overall survival, intraoperative blood loss, length of the operation and postoperative morbidity (especially postoperative ileus). The planned sample size is 250 patients (125 for complete removal of the omentum and 125 for preservation of the omentum) to determine whether omentum-preserving gastrectomy may be a candidate procedure for a Phase III trial in a randomized Phase II setting.