The adhesional function to blood vessel endothelial cells was evaluated in 2 cultured canine mammary gland tumor cells, CHMp and CHMm, derived from the primary and the metastatic lesion of the same patient. They exhibited negative (CHMp) and positive (CHMm) expression of sialyl Lewis X [sLe(x)], respectively. In the cell adhesion assay, the number of attached CHMm cells to human umbilical vein endothelial cells which expressed activated E-selectin was significantly increased. The process of cell-cell adhesion under flow conditions was observed only in CHMm cells. CHMm cells were revealed to have the adhesional ability to blood vessel endothelial cells and this adhesional ability was thought to be induced by the sLe(x)-E-selectin binding.