More than 1,000 species of predaceous mites exist, and a significant number may have the potential for application in plant protection. Currently, ≈15 species are available commercially, but only 2 or 3 are used in substantial quantities in North America. Commercial use of predaceous mites has been successful on greenhouse vegetables in Europe and Canada and on strawberries in California, but such use on ornamental plants is quite limited. Additional investigations are needed for most potentially useful predaceous species to elucidate life histories (especially intrinsic rate of increase, net reproductive rate, and cohort generation time), predator–prey interactions, and the influence of food, temperature, humidity, and host plant on survival and reproduction rates; as well as to develop mass rearing techniques and release strategies and tactics. Also needed is the development of selective insecticides for secondary pests and development of pesticide-resistant strains of predaceous mites. Although the knowledge base is limited and there are other constraints to the practical use of predaceous mites on ornamental plants, some progress is being made. For example, the practical use of Phytoseiulus persimilis Athias-Henriot against the twospotted spider mite, Tetranychus urticae Koch, on shade-grown palms in Florida has become a reality for ≈30 growers. A primary user of P. persimilis reported that a biological-control-based program using predaceous mites on palms reduced pest-control costs by 50%. Expanded use of predaceous mites on commercially grown ornamentals can be achieved through an intensified research and development program consisting of mission-oriented basic research, developmental research to advance techniques and operational guidelines, and large-scale adaptive pilot research that will lead to implementation under commercial conditions. Such efforts must be integrated with educational programs involving extension agents, growers, retailers, and consumers. The requisite resources must be assembled and mobilized through partnerships and joint ventures with contributions from the public sector, scientists, and industry.