At the time of diagnosis, gastric cancers are localized and surgically resectable in approximately 50% of patients; however, regional nodal metastases or direct invasion of surrounding organs or structures are frequently encountered and preclude cure by surgery alone in many patients. Analyses of patterns of relapse after complete surgical resection demonstrate that subsequent relapse of cancer is common in both the tumor bed and nodal regions as well as systemically. The standard of care for resectable gastric cancer for patients who can tolerate a surgical procedure is surgical resection. For patients with lower risk lesions (confined to gastric wall, nodes negative; T1–2N0M0 adjuvant treatment is usually not recommended except in select instances. Because both local and systemic relapses are common after resection of high-risk gastric cancers (beyond wall, nodes positive, or both; T3–4N0, TanyN+), adjuvant treatment is indicated for these patients. The results of phase III trials that demonstrate a survival benefit for preoperative irradiation, postoperative chemoradiation, or perioperative chemotherapy with epirubicin, cisplatin, and continuous-infusion 5-FU (ECF) versus surgery alone will be summarized and future trial designs will be discussed.