A rice bran 57-kDa protein was isolated by affinity chromatography with fibronectin immobilized on agarose. This fibronectin-binding protein designated as RB-57 had an amino-terminal amino acid sequence identical with that of a putative mature form of rice hydroxyproline-rich glycoprotein. A distinct feature of the amino acid composition of RB-57 was the high contents of hydroxyproline and proline representing about 45% of the total amino acids. The sugar analysis indicated that arabinose represented 46.8% of the total carbohydrates. RB-57 showed cell adhesion activity for murine Lewis lung carcinoma cells. The result suggests that RE-57 may play a role in plant cell adhesion, although cell adhesion-promoting activity for plant cells remains to be tested.