The ovary, uterus or ovary and uterus were autotransplanted to the neck of the ewe. The success rate in transplanting the ovary alone (17/22) or the ovary with the uterus (7/9) was much higher than transplantation of the uterus alone (3/8). Angiographic evidence was obtained for the patency of the uterine and ovarian arteries anastomosed to the carotid artery and utero-ovarian vein anastomosed to the jugular vein in ewes with all three types of autotransplants. Ewes with utero-ovarian autotransplants showed regular oestrous cycles and had normal luteal phases, as judged by the pattern of progesterone concentration in peripheral jugular venous plasma. However, ewes with ovarian autotransplants failed to show oestrus due to maintenance of the corpus luteum as indicated by the fact that the concentration of progesterone remained elevated for up to 220 days. The relatively high success rate in this series indicates that more extensive use could be made of these techniques.