Insecticide resistance is a threat to any long-term mosquito control program that relies on chemical insecticides. Since 1999 a state-wide program of training workshops has significantly increased the number of mosquito control programs that include regular monitoring of mosquito response to the active ingredients of the major “off the shelf” chemicals currently in use in Florida. To date, a standardized general procedure for insecticide resistance testing by the bottle bioassay has been published along with 13 technical memoranda that provide details how to prepare test solutions for the bottle bioassay. The bioassay is based on exposure of adult mosquitoes to a diagnostic concentration of insecticide that is selected to discriminate between fully susceptible mosquitoes from those that show some level of genetic resistance. The bottle bioassay allows the addition of synergists that interfere with specific metabolic pathways that degrade insecticides, thereby helping elucidate potential mechanisms of resistance. Specific examples of insecticide resistance and remedial actions taken will be provided.