Polypeptides from purified virions of the calf rotavirus (RV) isolate 993/83 and those from the pigeon RV isolate PO-13 comigrated on SDS-polyacrylamide gels. Two polypeptides of 45K and 47K were detected at the position of VP6. Both proteins behaved like authentic VP6 protein with EDTA and heat treatment. RV 993/83 and PO-13 showed identical one-dimensional peptide maps for VP2, and the 45K and 47K proteins. More than 70% of sera from German cattle older than 1 year showed neutralizing serum antibodies to RV 993/83 and RV PO-13.