Kunjin (KUN) virus has long been considered an arbovirus of minor medical and veterinary significance in Australia, with human infections associated with a mild febrile illness and rare reports of encephalitis in both horses and man. However its close relationship to a more virulent Australian arbovirus, Murray Valley encephalitis (MVE) virus, in terms of epidemiology, ecology and cross-reactivity in traditional serological diagnostic assays has necessitated that the activity of both viruses be carefully monitored in surveillance of mosquito-borne viruses in Australia. For a thorough discussion on the history, ecology and epidemiology of MVE and KUN viruses the reader is referred to an extensive review by Marshall (1988).Of more recent relevance, are the outbreaks of a fatal viral encephalitis in Europe, Russia, North America and the Middle East caused by strains of West Nile (WN) virus shown to be genetically closely related to KUN virus (Tsai et al. 1998; Briese et al. 1999; Jia et al. 1999; Lanciotti et al. 1999; Platonov et al. 2001; Hindiyeh et al. 2001). These events have stimulated additional interest in WN virus and its relationship to KUN virus with respect to taxonomy, and clinical and ecological comparisons. The purpose of this report is to review briefly the ecology and epidemiology of KUN virus, and to discuss methods of surveillance, diagnosis and control, with pertinent comparisons to WN and MVE viruses. Brief reference will also be made to the recent changes in the phylogeny and taxonomy of KUN in relation to WN virus; however, this aspect is covered in depth by Scherret et al., in this volume. KeywordsWest Nile VirusJapanese EncephalitisWestern AustraliaJapanese Encephalitis VirusArbovirus InfectionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.