Supplementation with folic acid and iron is recommended for pregnant women in order to prevent them from developing anemia. In malaria endemic areas of Africa, the World Health Organization (WHO) now recommends that pregnant women should also be given sulfadoxine-pyrimethamine (SP) once a month after quickening to protect them against malaria which is especially harmful during pregnancy. However, folic acid is an antagonist of SP so there is a possibility that giving folic acid with SP could interfere with the ability of the latter to provide protection against malaria. To investigate this possibility Gambian primigravidae with malaria parasitemia have been given SP and folic acid at the same time or on separate occasions two weeks apart and the ability of SP to cure the malaria infection investigated.