Abstract
Summary Malaria suppression by pyrimethamine, chloroquine and the two combined, administered at monthly intervals, was attempted in West African school children. Primaquine given at weekly intervals was also tested. Effective suppression was achieved in children receiving pyrimethamine alone and in combination with chloroquine; chloroquine alone was not found to be as efficient. Primaquine in weekly doses showed little or no effect on asexual parasitemia. There was an apparent inhibition of gametocyte production in children given the drugs. There was no evidence that the spleen rate or average enlarged spleen were affected by the treatment. The development of pyrimethamine-resistant strains was not observed throughout the six to eight month periods of the experiment.