CorM is a lectin isolated from the eggs of the fish Coregonus lavaretus maraena (Salmonidae family). The molecular weight of the subunits estimated by electrophoresis in the presence of dodecyl sulfate is 27 000 for both reduced and nonreduced substance. The lectin contains a large amount of cysteine, has a small content of aromatic amino acids, 10.4% of neutral sugar and 0.145% of Zn. It agglutinates specifically human B-group erythrocytes; the agglutination is stimulated by Zn2+and Mg2+ ions and partially inhibited by EDTA. The most efficient carbohydrate inhibitors are methyl alpha-L-rhamnoside, L-rhamnose, and raffinose (1).