[en] This study is carried out to determine ovine pregnancy associated glycoprotein (oPAG) levels in the serum of Berrichone ewes throughout gestation and the first month post partum. The levels were determinated with heterologous RIA using bovine PAG as standard and tracer and rabbit antiserum against oPAG. The level of oPAG increased from the 4th week of pregnancy till 12-13th week and decreased slowly till 17th week, when increased rapidly and reached the highest level (around 600-700 ng/ml). In the sheep carrying twins, we observed higher levels of oPAG than in the uniparous sheep. After lambing, oPAG decreased rapidly in 4 week to basal values. The oPAG concentrations in the animals carrying twins was higher when comparised to single lamb. We concluded that the oPAG level depends on the number of lambs and term of pregnancy. The estimation of oPAG concentrations in the blood can be used as a indicator for pregnancy diagnosis.