A novel 36kDa rhamnose-binding lectin isolated from Plecoglossus altivelis roe (PA 36), a probe for L-rhamnose and α-D-galactosyl nonreducing termini, bound to and agglutinated murine tumor cells rather than human type B erythrocytes. PA 36 was purified by DEAE-cellulose ion exchange and rhamnose-Sepharose affinity chromatography. The most effective saccharide in the agglutination inhibition assay was L-rhamnose. The α-D-galactosyl containing saccharides, such as melibiose, raffinose and stachyose, were more effective than the β-D-galactosyl containing saccharide, lactose. Lectin binding glycoproteins were determined by SDS-PAGE and blotting, followed by reaction with horseradish peroxidase-labeled PA 36. The glycoproteins ranging in molecular weight from 66, 000 to 72, 000 and deriving from murine tumor cells and bands 4.1 and 4.2 deriving from human type B erythrocytes were PA 36-binding glycoproteins. These results raise the possibility that nonreducing terminal α-D-galactosyl-containing glycoproteins composed of heterogeneous carbohydrate chains may be present on the surface of a number of different murine tumor cells as well as on human type B erythrocytes.