A knowledge of the exact length of the breeding season for improved breeds under different environmental conditions in this country is lacking. Such knowledge is of importance so that the lambing season can be arranged according to farm conditions. Such knowledge, apart from providing the necessary background for the successful application of artificial insemination and administration of hormones, helps to explain certain problems of infertility. By selection it should be possible to build up strains, by extending the breeding season at one or both ends, so as to get lambing at any required time. As the results below show, crossbreeding and selection could lead to early sexual maturity, prolonged breeding season or restricted lactation anoestrus, which would undoubtedly increase the reproductive potentiality of the ewe.