Adhesion molecules associating with peritoneal dissemination were investigated using human gastric (MKN45 and MKN74) and colon (KM12C and KM12SM) cancer cells and the mouse peritoneum. Adhesion of cancer cells to the peritoneum was determined by a recently reported novel ex vivo method. MKN45 cells established from poorly differentiated adenocarcinoma with less glycosylated sugar chains on their cell surface showed higher adhesion activities to the peritoneum ex vivo and produced large amount of metastases in the abdominal cavity of nude mice, whereas MKN74 cells from differentiated adenocarcinoma with more glycosylated sugar chains showed slightly low adhesion activity. KM12SM cells with highly metastatic potential to liver showed fairly low adhesion activity to the peritoneum compared with KM12C cells. The mouse peritoneum was found to contain alpha 1 --> 2, alpha 1 --> 3, and alpha 1 --> 4 fucosyltransferases, and adhesion of cancer cells was observed to the cellulose ester membrane, on which partially purified alpha-fucosyltransferases from mouse peritoneum were immobilized. The adhesion of cancer cells to fucosyltransferase-immobilized membrane was specifically inhibited by the addition of oligosaccharides and glycoproteins, which could serve as substrates for alpha-fucosyltransferases. These results indicate the contribution of alpha-fucosyltransferases to the adhesion of disseminated cancer cells to the peritoneum and support the possibility of antiadhesion therapy of peritoneal dissemination by treatment with substrates for alpha-fucosyltransferases.