This is a study of the efficacy and effectiveness of combination therapy for malaria due to P. falciparum in the Loreto Department, Iquitos, Peru. The investigators will enroll subjects ≥ 1 year-old who have a diagnosis of uncomplicated malaria due to P. falciparum. Patients will receive a treatment regimen consisting of mefloquine (25 mg/kg per day for two days) and artesunate (12 mg/kg per day for three days). Patients will be divided into two groups: one will receive drugs under direct supervision and the other will be instructed on how to take the drugs by themselves. Clinical and parasitologic response will be monitored for a follow-up period of 28 days. The findings of this study will be used to guide the Ministry of Health in evaluating its national policy for P. falciparum malaria treatment.