A recent study has shown that the administration of a single dose of sulfadoxine/pyrimethamine plus artesunate to Senegalese children on three occasions during a short malaria transmission season reduced the incidence of clinical attacks of malaria by 86%. However, use of this drug regimen led to the selection of parasites with molecular markers of resistance to pyrimethamine and sulfadoxine. Therefore, a trial of three alternative regimens has been undertaken to see if these are as effective and safe as the drug combination used in the initial study but less likely to select for drug resistance.