Two experiments were carried out on ewes with ovarian autotransplants to estimate the ovarian uptake of glucose and production of lactate. The first was carried out in the luteal phase of the oestrous cycle. Samples of carotid arterial, ovarian venous and jugular venous blood were collected simultaneously for glucose analysis. The arterial concentration of glucose (58.0 +/- 5.0mg/dL; Mean+/-SEM) was significantly higher than the ovarian venous concentration (42.3+/-2.4 mg/dL; P<0.001). Next, a second more complete experiment was carried out in the luteal and follicular phases of the oestrous cycle. The oestrous cycle was synchronised and samples of carotid arterial, ovarian venous and jugular venous blood were collected simultaneously for glucose and lactate analysis. There were significant positive arterio-venous differences in the concentration of glucose in the luteal (5.6+/-1.2mg/dL, mean+/-SEM; P=0.001), early (3.1+/-0.82 mg/d; P=0.003) and late follicular (6.4+/-1.3mg/dL; P=0.001) phases of the oestrous cycle. There was a significant negative arterio-ovarian venous difference in the concentration of lactate in only the luteal phase (-2.2+/-0.96 mg/dL; P=0.043). The results show significant removal of glucose from the arterial circulation during its passage through the ovary in the luteal, early follicular and late follicular phases of the oestrous cycle. Furthermore, there was lactate production in the luteal phase but not in the follicular phase suggesting that in the luteal phase of the oestrous cycle, ovarian metabolism can be anaerobic.