Some of the alternative treatments to avoid termination of pregnancy in cases where the fetus is affected by toxoplasmosis is to treat it as soon as the diagnosis has been made. The authors who already have experience of using pyrimethamine with sulfadoxoine (Fansidar) in the post-natal treatment of congenital infection, thought after reviewing the literature that this association of drugs would be harmless if applied during pregnancy. The principal risk that arises in the fetus is the teratogenicity of each of the components of pyrimethamine and sulfadoxine and also their associations. In animals pyrimethamine can increase the frequency of cleft palates probably because of its antifolinic action but there is no formal proof that it is teratogenic in human beings. Furthermore, the theoretical risk of karnicerus in the new born using the Sulfonamide has not been demonstrated. In the mother the main but rare risk (1 in 75,000) seems to be for the production of severe skin lesions such as Lyell and Stevens-Johnson which could be brought about by sulfonamides, but not particularly sulfadoxine.