This essay reviews advances in the systematics of mite families containing members that are acarine biocontrol agents (ABAs), including the Phytoseiidae which have several strains or races. Additions to the roster of mites that affect pests (including weeds and pathogens), and of pests that may be, or are, significantly affected by ABAs, were noted. The various pest-debilitating mechanisms used by ABAs, including predation, parasitism, parasitoidism, parasiticcastration, competition as well as reductions in weed and phytopathogenic fungal growth are listed. Theaffected targets include agricultural, veterinary and medical pests, as well as weeds, nematodes and fungi. The effect of intra-guild predation on the ABAs’ ability to affect pests is discussed, along with other organisms that increase the controlling impact of ABAs. The influence of host plants, including their architecture, leaf surfaces, domatia, pollen, genetically modified plants (GMOs) and volatiles are then reviewed. Then come mite feeding on soil-inhabiting pests and the newly-discovered effects of arbuscular mycorrhizal (AM) fungi. ABA feeding on weeds and on nematodes is briefly discussed next, along with the few known ABA diseases. The effect of plant-protection chemicals are then considered, followed by new techniques for the better implementation of ABAs. These include mass rearing, modes of distribution, long-term maintenance and the application of molecular methods to determine quantitative and qualitative feeding rates. This review ends with suggestions for further research, including more collecting and assaying of ABAs (especially indigenous species), determining the effects of secondary predators and of light regimes in greenhouses, and increasing studies on the role of volatiles of plant and nematode source, and of ABAs as vectors of pest diseases.