On the occasion of the thirty-five years of systematic research of toxoplasmosis, a review of the present knowledge of the role of toxoplasmosis in pregnancy is presented. Diagnostic procedures and the interpretation of the results of laboratory examinations are particularly stressed. The main conclusion is that in a population exposed to the infection in the way as was in the cases studied, the prevention of congenital toxoplasmosis can be achieved through a serologic follow-up of all pregnant women starting from the moment when pregnancy is established. The purpose of such screening is to identify those pregnant women who are not immunized (who are then advised to follow certain hygienic and dietetic measures) and those who are primoinfected in pregnancy. As the latter are at risk for transmitting the infection to their fetuses, they receive specific therapy and their fetuses are carefully controlled by ultrasound and other methods for the antenatal diagnosis of intrauterine infection.