The reaction of hemagglutination with trypsin-treated rabbit erythrocytes was used to reveal lectins on the cell surface of methanotrophic bacteria and in their culture liquids. By this method, no lectins were detected on the cell surface of Methylococcus capsulatus IMV B-3001 and Methylomonas rubra IMV B-3075 or in the culture liquid of any of the species studied. With intact cells of Methylocystis parvus IMV B-3491, the positive hemagglutination reaction observed was nonspecific and most probably occurred due to the high cell surface hydrophobicity characteristic of this species.