Serum carcinoembryonic antigen (CEA) levels were measured by radioimmunoassay in 82 patients with stomach cancer and were related to their clinical status and to the response to therapeutic modalities. Serum CEA in patients over 40 years of age was higher (p < 0.05) than that of younger age group and was higher (p 앞 0.0025) in patients with advanced stages (IIII and IV) than in patients with earlier stages (EGC and stage II). No significant differences in serum CEA levels were seen between the tumor cell types. In 9 patients who underwent successful radical resection of the cancer, serum CEA decreased significantly (p < 0.05) after surgery, whereas the changes in serum CEA levels after palliative surgery in other 7 patients were statistically insignificant (p > 0.01). Eleven patients who were given chemotherapy were followed up until death, the changes in their serum CEA levels were significant reverse-correlation (r=-0.72) with duration of survival.