The Spanish Assaf sheep breed, original from Israel, was introduced in Spain in the seventy’s, with a exceptional diffusion in the Autonomous Region of Castilla-León, where the importance of this breed is showed by the high census and its contribution to the agrarian production. This dairy sheep breed presents a higher production level than others native races from this region. This implies a racial change in herds and in the traditional management system, based on intensive productions. However, the Spanish Assaf breed neither has been recognized nor coordinated by any official organization until some years ago, so there has not been applied a specific breeding program. Nowadays, breeders and Deputation of León have implemented an official milking recording system, and the collection of pedigree data for the flocks involved in the selection program. It has also been developed an artificial insemination system in order to obtain tested sires. Slight increases in the number of flocks and ewes in milking recording, milk production, artificial inseminated females and number of tested sires have been reached due to the selection scheme. In the next future, the obtainment of a genetic progress according to the hopes of the breeders association is expected.