Pigeon rotavirus strain PO-13, which was recently shown to be neutralized by a hyperimmune serum to the prototype serotype 7 virus Ch-2, showed a one-way neutralization cross with turkey rotavirus Ty-1. When its genome was compared by RNA-RNA hybridization under stringent conditions with those of avian and mammalian rotaviruses, PO-13 displayed a low to medium level of homology only with turkey rotavirus strains Ty-1 and Ty-3 but not with chicken rotavirus strain Ch-1. Furthermore, no homology was found between the PO-13 probe and genomic RNA from 11 rotavirus strains which originated from 6 different mammalian species and which represented 6 major mammalian serotypes (1-6).