The relative toxicity of flufenoxuron to the predatory mite, Ambiyseius womersleyi and the spider mites, Tetranychus urticae and T. kanzawai was evaluated. Adult females and eggs of three species were placed on bean leaf discs dipped in several concentrations of flufenoxuron. Flufenoxuron was much less toxic to A. womersleyi than to the spider mites. At concentrations of 12.5∼100 ppm, flufenoxuron did not significantly affect the Survival of A. womersleyi. At the above concentrations, 88∼96% of adult female predators remained alive, Moreover, reproduction was not significantly reduced at any of the concentrations tested. Flufenoxuron did not affect the hatch of A. womersleyi eggs or the development of surviving immature predators. Survival of immature predators decreased with increasing flufenoxuron concentration. However, 44∼92% of immature predators reached adulthood at 12.5∼100 ppm. Adult female predators survived on a diet of twos-potted spider mites intoxicated with flufenoxuron, and their fecundity and the sex-ratio of the progeny were not significantly affected. Flufenoxuron at selective sublethal concentrations (12.5∼25 ppm) could be of value in adjusting predator/prey ratio in integrated management of the spider mites.