Two spp. of Typhlodromus predatory on cyclamen mite, Tarsonemus pallidus. were found to have marked differences in tolerance to parathion. The more effective spp., Typhlodromus reticulatus and/or T. cucumeris. were very susceptible to either laboratory or field treatments of this acaricide, whereas T. occidentalis showed a high degree of tolerance. This fact is important in the clarification of field population data on the natural control of this pest by Typhlodromus.