In a 500 head dairy sheep flock in Northern Greece, massive abortions (60%) were observed at 110-130 days of gestation. Attempts were made to treat the abortions with oxytetracyclin L.A. 20% but they were not successful. Toxoplasmosis was confi rmed by laboratory examination of blood sera of ewes, aborted fetuses, and fetal brain samples. Th e remaining 200 pregnant sheep were divided in 2 groups of 100 ewes each. Animals of Group 1 were treated with 20 mg/kg b.w. sulfadimidine every other day 4 times, while the animals in Group 2 received 33 mg/kg b.w. sulfadimidine every other day 4 times via i.m. route. Considerable reductions in abortions were observed. Th e treatments were more eff ective in Group 2. Lactation started in both groups aft er treatment and satisfactory milk was produced.