Although the incidence and mortality rate of gastric cancer have been steadily declining, gastric cancer is still the fourth most common cancer in the world and more than 50% of cases occur in Eastern Asia. In Korea, gastric cancer is the second most common cancer and third cause of cancer related death. The standard surgical procedure for resectable advanced gastric cancer is D2 lymphadenectomy with radical gastrectomy. Even though R0 resection was completed, recurrence is relatively common, and contributes to the limited survival of the patients in gastric cancer. As a clinically relevant factor for detection of the recurrence, the presence of isolating tumor cells has been introduced and it is so called as ‘micrometastasis’. Numerous immunohistochemistry and molecular studies have shown that micrometastasis can be demonstrated not only in lymph nodes but also in such body compartments as the bone marrow, peritoneal cavity and blood. Herein, we review the current knowledge and evidence of the prognostic significance of micrometastasis in peritoneal, lymph node, bone marrow. Also, we discuss the current state of research on the circulating tumor cell in peripheral blood.