We studied the effects of 5 kinds of catechins on the adhesion of mouse lung carcinoma 3LL cells to the monolayer of bovine lung endothelial cells. (‐)‐Epicatechin gallate and (‐)‐epigallocatechin gallate were active in inhibiting the 3LL cell adhesion, while (+)‐catechin and (‐)‐epicatechin were inactive. (‐)‐Epigallocatechin showed a considerable cytotoxicity. These data suggest that the specific chemical structure is required to exert the inhibitory activity of catechins and the search for the cellular binding protein(s) bound to these inhibitory catechins would provide a clue to clarify the mechanism of interactions between tumor cells and endothelial cells.