The nucleotide sequence of the gene encoding the outer capsid glycoprotein, VP7, isolated from a reassortant human rotavirus, M3014, was determined. The deduced amino acid sequence exhibited significant identity to the VP7 from a standard strain belonging to serotype G4, although the antigenic regions of the M3014 VP7 resembled sequences from both serotype G4 and G9 viruses. However, reactivity with G4 or G9 serotype-specific monoclonal antibodies was not observed. We suggest that the M3014 VP7 was derived from sequential mutation of a G4-like progenitor gene resulting in a protein with novel antigenic properties.