In the genetic selection programme run by “cooperativa Carnes Oviaragon S.C.L”, the genetic trend for sheep directly produced by the selection programme with artificial insemination parents (AI) is +0,0105±0,0034 lambs per year (0,783% of the phenotypic mean). This shows that both the methodology of genetic valuation and the selection decisions are efficient to improve the genetic level of the animals. However, the genetic trend of the population in connected flocks is negative (-0,0065±0,0011), indicating its slow but steady deterioration. This tendency is partly to be blamed on the selection of breeding animals based on morphologic rather than genetic criteria, whereas the positive trend of sheep produced by AI is a consequence of the selection of stallions based on genetic criteria. As a conclusion, the selection programme is efficient in detecting animals with high genetic value for prolificacy which can be used as breeding stock and produce sheep with high phenotypic and genotypic value. However, the number of improved animals by the programme is not enough to stop the steady deterioration of the population, so it is suggested to progeny test more males and leave the descendents progeny of the improved ewes in the flocks and positive sires as natural service sires and dams in the commercial flocks.