It has been shown recently in a study conducted in the USA (INT0116) that postoperative, adjuvant chemoradiotherapy improves survival for patients with gastric cancer. This treatment is relatively new and there remains debate regarding the optimal chemotherapy regimen and the optimal method of radiotherapy delivery. This study will evaluate a new regimen of adjuvant chemoradiotherapy for gastric cancer that employs ECF chemotherapy as the systemic component given before and after concurrent chemoradiation with continuous infusional 5-fluorouracil. Patients receive one cycle of ECF, followed 28 days later by chemoradiotherapy to a radiation dose of 45 Gy in 25 fractions over 5 weeks, and then one month later two further cycles of ECF are given. All patients are treated using multiple-field conformal radiation techniques.