Eight viruses of the Corriparta serogroup (Reoviridae: Orbivirus) that were known to be heterogeneous on the basis of serology and polyacrylamide gel electrophoresis were examined by reciprocal RNA-RNA blot hybridization of genomic RNA. Conserved and variant genes were identified by the degree of hybridization between cognate genes of different isolates. The eight viruses were divided into three subsets on the basis of the number of shared genes. Four of the viruses, isolated in Australia, formed one subset of related isolates and shared five conserved genes. Another isolate, Acado, was variant in all 10 genes and was considered to be a second subset. The remaining three isolates formed a third subset and shared four conserved genes. Genes 1, 3 and 10 were the most variable among the Corriparta serogroup isolates. Subsets of isolates within a serogroup which are highly related in the majority of the 10 genes and less related to serogroup viruses in another subset have not been reported previously. The phylogenetic relationship of Corriparta serogroup members suggested by the blot hybridization data is not apparent in the current taxonomic classification of these viruses which is based primarily upon serological data. The hybridization data on the Corriparta serogroup viruses are discussed and contrasted with other Orbivirus serogroups which have been examined similarly.