The implications of the traditional breeding structure of Merino sheep are discussed. It is indicated that it is unacceptable that material from stud flocks have a greater genetic merit than animals from commercial flocks. A description of the scientific selection activities of the Breed Society for Performance Tested Merinos (B P M) and also the initial results obtained are given. A controlled progeny test, as designed for B.P.M for the practical determination of breeding progress as well as for the determination of genetic differences between flocks, is outlined This technique makes it possible to compare animals from different flocks directly with regard to their breeding value.