Antibodies to Toxoplasma gondii were measured before and after pregnancy in a 1:64 dilution of sera with the direct agglutination test in 1613 ewes from 18 farms in 8 different counties of Uruguay from 1992 to 1994. The overall seroprevalence increased from 28.7% before mating to 38.5% after lambing in 2.5 yr and thus, the incidence was 9.8%. Losses due to toxoplasmosis during pregnancy were estimated to be 1.4 to 3.9% of the total number of ewes investigated, amounting to approximately US$1.4-4.7 million for the whole country.