The bovine parvovirus (BPV) hemagglutinates human erythrocytes by binding to glycophorin A (GPA). The purpose of this study was to determine which carbohydrate on GPA binds BPV. Treatment of GPA with alpha2,3,-6,-8 neuraminidase eliminated binding of BPV to GPA. Beta-elimination of O-linked sialic acids on GPA eliminated binding, while removal of N-linked carbohydrates using the N-glycosidase PNGase F failed to eliminate binding. Treatment of GPA with a neuraminidase which specifically cleaved alpha2,3 glycosidic bonds eliminated BPV binding and, following this treatment, virus binding to GPA was restored by reconstitution of alpha2,3-linked neuraminic acids. These results indicated the O-linked alpha2,3 neuraminic acids of GPA bind BPV.