Seven populations of Trialeurodes vaporariorum Westwood, each with a different history of exposure to insecticides, were surveyed for resistance to dichlorvos, malathion, methomyl, permethrin, and resmethrin. Six populations were resistant to methomyl, and four were resistant to resmethrin; one, with a long history of insecticide exposure, was slightly resistant to dichlorvos and malathion. Permethrin was most effective, followed in order by resmethrin, methomyl, malathion, and dichlorvos. Adults were more susceptible than nymphs. The spectrum of resistance was generally consistent with the history of insecticide exposure.