The extent of genetic variation of rotavirus isolates representing the common serotype G1 circulating in Australian urban centres during 1996 was investigated. The sequences of the major outer capsid glycoprotein, VP7, of three isolates from Brisbane, Sydney and Melbourne were determined and found to be highly conserved (> 99% nucleotide identity, > 98.3% amino acid identity and > 99% amino acid similarity). In particular, the sequences of the neutralisation epitope regions were absolutely conserved. These strains and those from other cities were analysed by Northern blot hybridisation using a probe derived from a prototype serotype G1 virus. For all strains, the eleven genomic RNA segments hybridised with the probe indicating that these strains were not derived from genetic reassortment between different rotavirus geno-groups. These results suggest that, within a single epidemic season, rotavirus strains circulating in geographically diverse communities share common genetic features.