The aim of the study was to determine the effects of low energy diets on the enzymatic antioxidant activities of ewes in late pregnancy. Thirty Chios ewes were used. Twenty pregnant ewes were divided into 2 groups of 10 ewes each (groups II and III), with 10 non-pregnant ewes being separated into a third group (group I). The ewes in groups I, II and III were fed rations containing 9.14 MJ ME/kg of dry matter (DM)-10.23% crude protein (CP), 10.20 MJ ME/kg of DM-15.04% CP, and 8.82 MJ ME/kg of DM-14.47% CP, respectively. Plasma copper-zinc superoxide dismutase (Cu-Zn SOD), glutathione peroxiclase (GSH-Px), catalase (CAT) activities and thiobarbituric acid reactive substances (TBARS) concentrations were measured on days 105 and 148 of pregnancy. No significant differences for Cu-Zn SOD and TBARS were detected among the groups on days 105 and 148 of pregnancy. The catalase activities of group III were higher by P < 0.05 than those of both groups I and II on day 148 of pregnancy. The GSH-Px activities of group II were higher than those of group I on day 148 of pregnancy (P < 0.05). In a 2-day comparison of each group, only GSH-Px activities increased in group [if (P < 0.05). It was concluded that the reason for the high plasma CAT and GSH-Px activities at the end of pregnancy is to protect the foetus from the deleterious effects of hydrogen peroxide.