The primary objective of the study was to determine whether the administration of one dose of sulfadoxine-pyrimethamine plus artesunate to Senegalese children aged 6 weeks to 59 months on three occasions during the malaria transmission season would reduce significantly the incidence of clinical attacks of malaria. Secondary objectives were determination of the incidence of side effects in children who received IPTc; the impact of IPTc on the prevalence of molecular markers of resistance to SP in samples positive for Plasmodium falciparum; and the effects of IPTc on the incidence of malaria in the rainy season following the intervention.