It is important to develop an efficient adjuvant therapy for the prevention of the postoperative peritoneal recurrence of gastrointestinal cancers such as gastric cancer or pancreatic cancer. Milky sports (MS) are peritoneal lymphoid tissues broadly distributed on the peritoneal tissues such as the omentum, mesentery, or Douglas pouch, and are the selective implantation sites of disseminated cancer cells. In this study, we introduced GFP gene into various cancer cell lines and host-derived cells such as peritoneal macrophages and dendritic cells by adenovirus vetor and injected them i.p. into mice. We then investigated the sites of GFP expression on the peritoneum by fluorescence microscopy. The results showed that green fluorescence was detected specifically for the MS sites that stained black with activated carbon particles (CH40), despite the differences in the cell type injected. These findings indicate that 1) the physioanatomical characteristics of MS may play an essential role in the formation of the initial disseminated lesions at MS, and 2) the host-derived cells accumulating near MS may be available as carriers of a therapeutic gene in intraperitoneal gene therapy against peritoneal dissemination.