A total of 698 blood serum samples from sheep in various regions of the People's Republic of Bulgaria were examined throught the indirect hemaglutination micromethod. Two-hundred and seventeen proved positive for toxoplasmosis. Those of the samples that were taken from ewes that had miscarried and reacted positively were considerably more--43.3 per cent--than those that were taken from ewes with normal lambing and reacted positively--21 percent. Besides, toxoplasmosis was shown to be more widely spread among sheep in the mountainous regions (40.3 per cent) than in sheep from the plain regions (18.3 per cen). Four cystogenic strains of Toxoplasma were isolated from fetuses of nine ewes that had miscarried. Out of 493 sheep investigated in Czechoslovakia 33.3 per cent were positive by the indirect hemagglutination reaction, 29.7 per cent were positive by the indirect fluorescence reaction (RIF), and 11.6 per cent were positive by thr microprecipitation agar gel reaction (MPA). States is the epizootiologic and economic importance of the problem.