SummaryCurrent practices for early warning of activity of Murray Valley encephalitis and other medically‐important arboviruses are reviewed with view to improvement. Data From previous papers onCulex annulirostrispopulations, environmental factors and virus infection rates were reanalysed and the results considered as a basis for prediction and surveillance. This goal will only be achieved with improved national cooperation, a better epidemiological understanding and greater knowledge of the bionomics of the major vector,Culex annuliroslris. The improved monitoring system will utilize meteorological, serological and entomological criteria.