The structural glycoproteins of calf (BDV 486), human (Wa) and simian (SA11) rotaviruses were compared for sensitivity to endoglycosidase (Endo) H. The calf and human virus glycoproteins were reduced by approximately 5000 molecular weight in two equal stages. The simian rotavirus glycoprotein sustained only one 2500 molecular weight decrease. The effect of the host cell on the viral oligosaccharide composition was examined. Endo H digests of calf rotavirus 82-124 extracted from stool and its progeny propagated and [35S]methionine-labelled in MA104 cells were compared. Endo H had the same effects on the glycoproteins, indicating that the nature of the host cell does not affect the oligosaccharide composition of the virus glycoproteins.