Methods: An in vivo antimalarial drug efficacy trial will be conducted in three areas of the Philippines. Subjects > 6 months of age with parasitologically confirmed, uncomplicated P. falciparum infections will be recruited. Patients will be treated with single dose SP (25 mg/kg of the sulfadoxine component in a single dose) plus CQ (25 mg/kg over three days) or artemether + lumefantrine (twice daily) over 3 days. Patients will be randomly assigned one of the two drugs regimens. Clinical and parasitological parameters will be monitored over a 28-day follow-up period to evaluate drug efficacy. Results from this study will be used to assist the DOH in assessing their national malaria treatment policy for P. falciparum malaria.