Acute falciparum malaria is associated with low plasma arginine and impaired nitric oxide (NO) production. Both are associated with poor outcome. This study will examine the safety and effect of escalating doses of arginine in falciparum malaria. It will determine whether arginine can increase NO production and have an effect on NO-dependent physiological measurements. The hypothesis is that arginine: will be safe in falciparum malaria; will return plasma arginine concentration to normal/supranormal levels; will increase systemic and exhaled NO; reduces oxidant stress; and improves a number of NO-dependent physiological measures of relevance to malaria.