The design of orchard pest control programs that favor natural enemies is based partly on a knowledge of the toxicity of spray chemicals to beneficial arthropods. This paper summarizes the results of tests conducted during the past five years to determine toxicities, and it includes some previously published data (MacPhee and Sanford 1954 and 1956). Tests were discontinued after 1955 on the species Stethorus punctum (Lec.), Euderus spp., Scambus spp., and Trichograma minutum Riley and on the chemical formulations Aramite, Chlorocide, Erad, fixed nicotine, lime sulphur, Puratized Agricultural Spray, summer oil, and synthetic cryolite. Tests were initiated on the phytoseiids Typhlodromus finlandicus (Oudms.) and T. rhenanus (Oudms.), and the mirid Psallus sp., and also on the pesticides Bacillus thuringiensis Berliner preparation, demeton, Diazinon, dodine, Kelthane, Kepone, Rhothane, Sevin, Tedion, Trithion and zineb. Typhlodromus pyri Scheuten was previously reported as T. tiliae (Oudms.), a synonym, and Atractotomus mali (Meyer) is an authoritative identification of the species previously listed as Criocoris saliens (Reuter).