Treatment of uncomplicated P.falciparum malaria with sulfadoxine-pyrimethamine (SP) is followed by a marked increase in the density of gametocytes. To determine whether treatment with SP enhances gametocyte carriage, we randomized asymptomatic carriers of P.falciparum to receive SP alone, SP with a single dose of artesunate, or placebo, and followed them for 56 days to record gametocyte presence and density.