This is a multi-center, prospective phase II trial. Patients with histologically proven nonresectable or recurrent/metastatic gastric adenocarcinoma, with at least one measurable lesion, no prior chemotherapy or radiotherapy, and adequate baseline organ functions will be eligible. Cetuximab (Erbitux; Merck, Germany) 400 mg/m2 will be given as an intravenous (IV) infusion, initially (i.e., day 1 of cycle 1); and then followed by weekly IV infusions of cetuximab 250 mg/m2 (i.e., days 8, 15, 22 of cycle 1, and days 1, 8, 15, 22 of cycle 2 and subsequent 28-day cycles). Cisplatin will be given as a 24-hour continuous IV infusion in a dose of 35 mg/m2/day, admixing with 5-FU 2,000 mg/m2 and leucovorin (folinic acid) 300 mg/m2, day 1 and day 8. A 24-hour continuous IV infusion of 5-FU 2,000 mg/m2 and leucovorin 300 mg/m2 will be given on day 15. The cycles will be repeated every 28 days, and the response evaluation will be performed every two cycles and at the end of protocol treatment. Confirmed objective response rate by RECIST (Response Evaluation Criteria in Solid Tumors) will be the primary end-point. Using the Simon two-stage design for phase II study (P1 - P0 = 0.20 with the response rates of interest being P0 = 60% and P1 = 80%), a total of 35 patients are planned to be enrolled in an estimated enrollment period of 12 to 18 months.