The dispersal of Culex annulirostris, a major arbovirus vector in Australia, was studied in Griffith, N.S.W. using a mark-release-recapture technique. From an empirical model of dispersal, fitted to data on recaptured adults, the average distance dispersed was 6.8 km (95% c.l. 4.1-40.9 km), and 50% of the population dispersed 4.8 km or more. Maximum recorded dispersal was 8.7 km, and 2 individuals traveled more than 5 km in 1 day. The relevance of the findings to control strategy is discussed.