The oestrous cycles of Karakul ewes were synchronized during both the breeding (February) and non breeding season (October) using either whole or halved sponges, in combination with either subcutaneous or intravenous administration of PMSG. At the time of sponge withdrawal, PMSG was administered either subcutaneously or intravenously at one of 4 levels, 0; 60; 150 or 300 I.U. The interval between sponge withdrawal and the onset of oestrus, as well as the number of ovulations per ewe, were recorded. Lambing percentage after using artificial insemination was determined only in the nonbreeding season. Only the season of treatment had an effect on the percentage ewes showing oestrus. The time interval between progestogen withdrawal and the onset of oestrus was significantly (P ≤0,05) shortened in groups synchronized with halved sponges, groups receiving PMSG intravenously and groups receiving PMSG doses higher than 60 I.U. Ovulation rate was not significantly affected by the progestogen treatments. However, there was some tendency for a higher ovulation rate with the higher doses of PMSG. The lambing percentage of ewes synchronized with whole sponges and ewes receiving PMSG intravenously, was superior to the other treatment groups.