In this thesis the results of a large-scale study of preventive measures against toxoplasma infections in pregnant women are reported. Literature on Toxoplasma gondii, toxoplasma infections and toxoplasmosis is discussed in chapter 1. Special attention is directed toward the epidemiological aspects as they relate to the possibilities of preventing congenital toxoplasmosis. The historical background is presented as an introduction to the actual study. The initial aim of separate evaluation of primary and secondary prevention had to be abandoned due to various circumstances. As a result, the study was finally designed to evaluate the simultaneous application of both primary and secondary preventive measures in order to be able to establish guidelines and prerequisites for a future national preventive programme ; Since no effective therapy is available to prevent manifestations of congenital toxoplasmosis, prevention is the strategy par excellence to control congenital toxoplasmosis. The World Health Organization in Europe recommended that all countries consider the possibilities of a preventive programme; the programmes in France and Austria were cited as examples of successful disease controL At about the same time the Health Council in the Netherlands recommended a trial study. In the study described here both primary and secondary prevention were applied: repeated serological control of initially seronegative women allowed assessment of the incidence of primary infections during pregnancy when primary preventive measures were emphasized. In this chapter different strategies to prevent congenital toxoplasmosis in the Netherlands will be discussed