Prevention of connatal toxoplasmosis is only possible by early diagnosis and treatment of toxoplasma-primoinfection in pregnancy. The authors describe the diagnostic approach and report on 110 pregnant women with toxoplasma-primoinfection. Treatment consisted in the application of pyrimethamine in combination with a sulfonamide or spiramycine. Side-effects of pyrimethamine are mentioned. The aim is an improvement of diagnosis and therapy.