Pregnant Chios ewes with high twin-lambing rates fed a low energy ration during the final periods of pregnancy were studied. The aim of this study was to determine whether pregnancy toxemia occurred in these ewes by monitoring the changes in the concentrations of serum free fatty acids (FFAs), plasma beta-hydroxybutyrate (beta-HB) and urea. Thirty-eight Chios ewes were used. The animals were divided into 3 groups: pregnant normal energy (PNE), pregnant low energy (PLE), and non-pregnant normal energy (N-PNE). On day 105 of gestation, the animals were begun to be fed with the treatment rations. The feeding regime was continued until lambing. Blood samples were taken into tubes with and without anticoagulant from the jugular vein on days 120, 127, 134, 141, and 148 during gestation. The ewes in PLE had higher concentrations of FFAs on days 134 and 148 compared to those in PNE. beta-HB concentrations in PLE animals were always higher than those in PNE. No difference was found between PNE animals and N-PNE animals. Plasma urea concentration in PNE decreased on day 127, and then continuously increased to a significant [eve] on day 148. It is concluded that an energy intake of greater than 10 MJ/kg ME should be ensured for pregnant ewes in late pregnancy, although an energy level of 8.0 MJ/kg ME does not cause a serious energy deficiency and does not cause pregnancy toxemia.