The tendency of honey bees, Apis mellifera L, to becomeinfested with tracheal mites, Acarapis woodi (Rennie), wasmeasured in six different types of F₁ colonies. Thecolonies were produced by mating a stock (Buckfast) known to resistmite infestation to each of five commercially available stocks and to astock known to be susceptible to mites. Young uninfested bees fromprogeny and parent colonies were simultaneously exposed to mites ininfested colonies, then retrieved and dissected to determine resultantmite infestations. Reduced infestations similar to but numericallygreater than those of the resistant parent bees occurred in each of thesix crosses made with resistant bees regardless of the relativesusceptibility of the other parental stock. Reciprocal crosses betweenresistant and susceptible queens and drones proved equally effective inimproving resistance. Therefore, allowing resistant stock queens tomate naturally with unselected drones, or nonresistant queens to matewith drones produced by pure or outcrossed resistant queens, can beused for improving resistance of production queens.