Eight strains of Boophilus decoloratus (Koch) are described from farms in the High veld area of Rhodesia. All eight strains showed resistance to a number of organophosphorus ixodicides and four showed additional resistance to the carbamate, carbaryl. This is the first recorded resistance to these two groups of ixodicides in Rhodesia.
Biochemical studies on the Alicedale West Farm strain indicated a level of resistance between that of the Berlin strain of B. decoloratus and the Biarra strain of B. microplus (Can.).