Very little is known of the origin of the Ronderib-Afrikaner sheep, but it is generally believed to have been developed by selection from the indigenous sheep of the fat-tailed type which were in the posession of the Hottentots when the Cape was first occupied in 1652. The Ronderib-Afrikaner is a very hardy breed and is to be found mostly in the dry North Western districts of the Cape Province. As the breed must of necessity continue to play an important part in the farming system of the more arid regions in the Union of South Africa, it was decided to obtain data on the age of sexual maturity, oestrous, the oestrous cycle, and the gestation period of these sheep. This publication deals only with the gestation period. The other aspects of the study on their sex-physiology will appear later.