16,733 pregnant women were studied for toxoplasma specific antibodies during an 18-month period. The number of specimens was 44,181. The IgG seropositivity of mothers was 20.3%. The incidence of primary toxoplasma infections during pregnancy was 4.2 per 1000 seronegative pregnancies by using the traditional criteria, IgG seroconversion and/or a positive IgM. By using the IgG activity test as an additional criterion, the incidence was 2.4 per 1000 seronegative pregnancies. Due to transmission rate of 40%, the number of congenital toxoplasma infections in Finland is more than 50 per year. The evaluation is going on and the cost-benefit analysis will reveal the effectiveness of antenatal screening.