Human colorectal carcinomas with increased metastatic potential and with poor prognosis are characterized by the high content of sialyl-LeX carbohydrate antigens. The levels of these carbohydrate antigens apparently increase during colorectal carcinoma progression from non-metastatic to metastatic tumors. The levels of tumor-associated sialyl-LeX antigens are inversely correlated to the post surgical survival of colon carcinoma patients as revealed by retrospective studies. Cell lines selected for high levels of cell surface sialyl-LeX antigens metastasize to livers when they are injected intrasplenically into nude mice. The highly expressing cells also strongly adhere to activated endothelial cells apparently through E-selectin. We conclude that sialyl-LeX carbohydrate antigen is a unique molecular phenotype that determines colorectal cancer metastasis.