Encephalitis vector surveillance (EVS) traps were used to study the attractant effect of CO2 and 1-octen-3-ol (octenol) on mosquitoes at 2 different locations in southeast Queensland. Octenol alone was only slightly attractive for Aedes vigilax. There was a significant increase in the numbers of Ae. vigilax and Aedes funereus caught when octenol was added to CO2, although catches of Culex annulirostris and Culex sitiens did not change significantly. The size and age compositions of Ae. vigilax attracted by CO2 and by octenol were comparable. These data suggest that octenol should be considered as a supplement to CO2-baited EVS traps for mosquito-based arbovirus surveillance in southeast Queensland.