Two human rotavirus strains, PCP 5 and MZ 58, which possessed an unusual combination of subgroup (I), serotype (3) and RNA pattern (long) were examined by RNA-RNA hybridization to determine their genogroup. While these two strains did not belong to either the Wa or the DS-1 genogroup, PCP 5 and MZ 58 possessed seven gene segments that formed hybrids with bovine rotavirus strain NCDV and four gene segments that formed hybrids with human rotavirus strain AU-1. These results suggest that PCP 5 and MZ 58 were intergenogroup reassortants formed in nature between a member of the bovine rotavirus genogroup and a member of the AU-1 genogroup.