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.

Inclusion Criteria:

• Pf monoinfection with asexual forms
• Parasite density of greater than 500 per mcl and less than 200 parasites per oil immersion field (MINSA quantification of "4 plus")
• Age > 6 months
• Temperature greater than 38C (101F)
• Available and willing to return for follow-up

Exclusion Criteria:

• Presence of any of the following "danger" signs or symptoms suggestive of severe malaria
• Not able to drink or breastfeed
• Repeated vomiting (unable to keep anything down)
• Convulsions during present illness
• Lethargic or unconscious state
• Unable to sit or stand up
• Respiratory distress
• Jaundice (observation) or dark urine (by history)
• Severe anemia (Hemoglobin < 5 g/dl)
• Hypotension (systolic BP < 80 mm Hg in adults and < 50 mm Hg in children under the age of 5
• Presence of another significant illness or chronic disease
• Known pregnancy (by history)
• History of hypersensitivity to medication used in the test