Current immunological and biochemical information regarding the hemagglutinin and virus-cell interactions of rotavirus is obtained exclusively from studies with group A rotaviruses. In this study, I report that the immunologically and genetically distinct group C rotavirus also possesses a hemagglutinin. The viral hemagglutinin was identified on a cultivable porcine group C rotavirus strain (strain AmC-1) by using agglutinated human and guinea pig erythrocytes. Neuraminidase treatment of fresh human erythrocytes or blocking with glycophorin A or fetuin prevented hemagglutination. Infection of swine testicular cells with group C AmC-1 virus was also prevented by glycophorin A, fetuin, and neuraminidase treatment, suggesting that sialic acid constitutes an essential part of the cell receptor.