The activity of several enzymes has been measured in the oviducal mucosa, endometrium, caruncles, cervical mucosa and vaginal mucosa as well as in uterine, cervical and oviducal rinsings of ewes at days 0 (oestrus), 1, 8 and 15 of the oestrous cycle.Acid phosphatase activity was maximal during the luteal phase in the oviduct, endometrium and cervix, but not in the vagina where the highest level was on day 1. Alkaline phosphatase activity showed a significant rise at mid-cycle in the endometrium and caruncles as did glucose-6-phosphate dehydrogenase activity in the endometrium.Glycogen (starch) synthase in the endometrium and cervical mucosa was greater at days 0 and 8 than at days 1 and 15. Vaginal and caruncular total glycogen (starch) synthase activity showed a significant rise at mid-cycle. Active and total glycogen phosphorylase activities were maximal on days 8 and 15 in the vagina. Glycogen concentration was greatest at days 8 and 15 in the cervix, while oviduct values were lower on day 1 than at oestrus or day 15.In the oviduct rinsings alkaline phosphatase activity was greatest at day 1, whereas in cervical rinsings the activities of acid and alkaline phosphatases were less at oestrus than at days 8 and 15. The glycogen phosphorylase and p-glucuronidase activities in uterine rinsings were greater at days 8 and 15 than at oestrus.