Pemetrexed has shown an anti-tumor activity in advanced gastric cancer patients in a previous study, while cisplatin is widely used in the combination chemotherapy of gastric cancer. Pemetrexed has shown synergy with cisplatin in preclinical models and in various human cancers. The introduction of vitamin supplementation has made treatment with pemetrexed plus cisplatin safe and well tolerated. The present phase 2 study is an effort to determine the efficacy and safety of the combination of pemetrexed and cisplatin in Korean patients with gastric carcinoma who had no prior palliative chemotherapy for advanced disease. The patients, who will give their consent for participating in this study, will be screened for their eligibility and on meeting pre-defined study eligibility criteria, they will receive an intravenous therapy of the combination of pemetrexed and cisplatin for number of times that in the opinion of their treating physician is appropriate for them. A response rate of 30% is considered as the minimum activity level of interest for this patient population.

Inclusion Criteria:

• diagnosis of adenocarcinoma of the stomach
• Stage IV disease not amenable to curative surgery.
• Disease status must be that of measurable disease as defined by RECIST criteria
• Performance Status of 0 or 1 on the ECOG Scale and adequate organ function.
• Signed informed consent from patient

Exclusion Criteria:

• Prior palliative chemotherapy for advanced disease.
• Known or suspected brain metastasis or Second primary malignancy that is clinically detectable at the time of consideration for study enrollment.
• Concurrent administration of any other tumor therapy
• Inability to interrupt aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) 2 days before, the day of, and 2 days after the dose of ALIMTA plus cisplatin.
• Inability or unwillingness to take folic acid, vitamin B12 supplementation, or dexamethasone.