The National Rotavirus Reference Centre, together with collaborating laboratories Australia-wide, has conducted rotavirus surveillance since June 1999. This report describes the serotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2002 to 30 June 2003. We examined 573 faecal samples using monoclonal antibody immunoassays, reverse transcription-polymerase chain reaction, and polyacrylamide gel analysis. For the second consecutive year, serotype G9 strains were the most prevalent type nationally (74.7%) and were found in all seven contributing centres. Serotype G1 strains were the second most prevalent type (11.3%), identified in four of the centres. These findings have implications for vaccine development strategies which have targeted protection of disease due to serotypes G1-G4.