Aedes aegypti larvae from Antigua, Jamaica, Puerto Rico, St. Lucia, Trinidad and Union Island and predatory larvae, Toxorhynchites moctezuma, from Trinidad were tested for susceptibility to temephos, malathion, fenthion, fenitrothion and chlorpyrifos. There was some organophosphorus resistance in all strains of Ae. aegypti, in the approximate order: Antigua greater than Jamaica greater than Puerto Rico greater than St. Lucia greater than Trinidad greater than Union Island. Toxorhynchites moctezuma was much less susceptible to temephos than the Ae. aegypti strain, indicating its possible usefulness in an integrated management program.