The ongoing national project for prevention of congenital toxoplasmosis has created a need for general information on both toxoplasmosis in relation to pregnancy and on congenital toxoplasmosis. This paper presents an up-to-date survey of these facts. It briefly describes the clinical picture and what can happen to the foetus after primary maternal infection. Special emphasis is placed on diagnosis, and recommendations are made for the treatment of infected mothers and babies. Prevention of congenital toxoplasmosis is discussed from both an individual point of view and in a social perspective.