Three geographical strains of Aedes aegypti from Thailand (Amphur), East Africa (Kampala), and the West Indies (Santo Domingo) were compared for susceptibility to infection with low-passage yellow fever virus (French viscerotropic) as well as for ability to transmit virus by bite at varying extrinsic incubation periods. Santo Domingo strain appeared the most competent and Kampala the least when mosquitoes were exposed to a low level virus-infecting blood meal; at higher virus levels, a similar trend was noted but differences were less evident and in no case were the differences statistically significant. All three strains were infected with and transmitted yellow fever virus.