Plasma progesterone profile was determined at various stages of pregnancy and at parturition in 30 Barki and Rahmani ewes during summer and winter. Progesterone level increased significantly (P < 0.01) with the advance of pregnancy. The sharpest rise occurred after day 70 during summer and after day 90 during winter with a sharp decline occurring during the last week before parturition; plasma progesterone remained low up to day 8 post-partum. Contrary to those for body weight gains, but similar to those for rectal temperature, the overall means of plasma progesterone were significantly higher (P < 0.01) in summer (6.04 ng/ml) than in winter (4.01 ng/ml). The effect of season on plasma progesterone levels was more pronounced in the Rahmani breed. The concentration of plasma progesterone can be used successfully to diagnose pregnancy in both Barki and Rahmani ewes 16 days after mating. Progesterone level over 1.5 to 2.0 ng/ml after day 16 can indicate a successful mating. In 1 Rahmani ewe which aborted on day 131 of pregnancy there was a slow decline in plasma progesterone level that continued for several weeks before abortion.