A certain percentage of patients with cancer suffer from recurrences following surgery with curative intent. This suggests the existence of isolated cancer cells and micrometastases that cannot be detected by routine preoperative imaging studies and intraoperative observations. Recently, such micrometastases have been detected from various clinical samples such as peripheral blood, bone marrow aspirates, lymph nodes, and peritoneal washes, using molecular biology techniques, and it is now possible to more accurately stage patients and individualize adjuvant treatment strategies based on the information obtained through these methods. The prognostic impact of detecting micrometastasis is highly variable and seems to depend on the type of cancer and the specimen from which it was detected. In this review,the authors describe the relevance of micrometastases detected in various body components of patients with gastric cancer, and propose how the information thus obtained could be reflected in the treatment strategy.