Median effective dosages (ED50) of the repellent diethyl toluamide and median lethal concentrations (LC50) of the insecticides DDT and malathion were determined for 13 strains of Anopheles albimanus, An. stephensi, An. quadrimaculatus, Aedes aegypti, Ae. taeniorhynchus, Culex tarsalis and Cx. pipiens. Correlations of the ED50's of diethyl toluamide with the LC50's of DDT and malathion were not statistically significant. The results indicate that diethyl toluamide would be equally effective against insecticide-susceptible mosquitoes in the field.