Book excerpt: Adjuvant chemotherapy is a standard treatment for operable gastric cancer. However, the preferred treatment varies by geographical region. Southwestern Oncology Group (SWOG) conducted a, randomized trial of adjuvant chemotherapy for patients with surgically resected gastric cancer. The 3-year survival rates were 50% in the chemoradiotherapygroup and 41% in the surgery group. The Medical Research Council Adjuvant Gastric Infusional Chemotherapy (MAGIC) trial that compared perioperative chemotherapy with the ECF regimen (epirubicin, cisplatin, and 5-fluorouracil) and patients with surgery alone had a 5-year survival rate of 36 and 23%. The Adjuvant Chemotherapy Trial of TS-1 for Gastric Cancer (ACTS-GC) showed that the 3-year overall survival rate was 80.1% in the S-1 group and 70.1% in the surgery-only group in stage II or III gastric cancer patients who underwent a D2 gastrectomy. An analysis of the Capecitabine and Oxaliplatin Adjuvant Study in Stomach Cancer (CLASSIC) study showed 3-year disease-free survival, 74% in the chemotherapy and surgery group and 59% in the surgery-only group in the patients with stage II,ÄìIIIB gastric cancer who had D2 gastrectomy. In conclusion, for all patients with stage II and III gastric cancer, standard D2 gastrectomy and adjuvant chemotherapy are strongly recommended for improved survival rates.