F, larvae and adults from wild populations of Aedes taeniorhynchus (Wied.) and Culex nigripalpus Theob. In Florida were tested against malathion, naled, and fenthion, and compared to the susceptible laboratory strains. The areas tested were based on previous results and also included new areas for additional susceptibility information. Both larvae and adult forms of Ae. taeniorhynchus were found to be resistant to malathion F, adults from one of the Florida Keys were 40 times more tolerant to malathion at the LC50 level based on paired tests with the laboratory susceptible strain. No resistance was detected when larvae or adults from some of these resistant areas were tested against naled or fenthion. F, larvae of Cx. nigripalpus were as susceptible as the laboratory strain when tested against malathion and naled; however, adults from some areas were up to 5X less susceptible to malathion.