OBJECTIVE To describe the actual and potential geographic distributions of Ixodes cornuatus and I holocyclus in south-eastern Australia. PROCEDURE Examination of ticks from museum collections and trapped animals were made. (Bioclimatic analysis BIOCLIM) was used to predict potential distributions. RESULTS I holocyclus was collected from rodents (Rattus fuscipes, R lutreolus, R rattus), wombats (Vombatus ursinus), cats and dogs in Gippsland and I cornuatus was collected from rodents (R fuscipes), wombats, cats and dogs in central Victoria. All life-cycle stages of both species were collected during the warmer months of the year. The known distribution of the two species was established from specimens in museum collections and suggested that a boundary between the two may exist in eastern Gippsland. BIOCLIM suggested that the area immediately to the east of Melbourne was climatically suitable for I holocyclus, although no endemic foci of infection are currently known from this region. The potential distribution of I cornuatus included east Gippsland and the Otway Ranges, areas in which the tick is not currently known to occur. CONCLUSIONS I holocyclus and I cornuatus have more restricted distributions than current collections suggest and therefore may have the possibility to extend their geographical ranges in the future.