The National Rotavirus Reference Centre together with collaborating laboratories Australia-wide has conducted rotavirus surveillance since June 1999. The serotypes of rotavirus strains that are responsible for the hospitalisation of children with acute gastroenteritis were determined for the period 1 June 2001 to 31 June 2002. We examined 754 rotavirus samples using a combination of monoclonal antibody immunoassay, reverse transcription-polymerase chain reaction, and Northern hybridisation. For the first time, serotype G9 strains were the most prevalent type nationally (40.4%) and found in 8 of the 9 centres. Serotype G1 strains were the second most prevalent type (38.9%), identified in 5 of the centres. These findings have important implications for vaccine development strategies which target serotypes G1-G4.