The purpose of this study is to determine the efficacy of pyrimethamine/sulfdoxine (Fansidar®) for the treatment of uncomplicated falciparum malaria in the Peruvian Amazon. Reports in the mid 1990s indicated that Fansidar was failing to cure patients with confirmed falciparum malaria. The study design was based on accepted WHO parasitological and clinical outcomes to determine the overall efficacy of Fansider and inform the Peruvian National Malaria Control authorities as to the continued wisdom of recommending Fansidar as first line treatment for uncomplicated falciparum malaria in the Peruvian Amazon.