Falciparum malaria infection is associated with significant destruction of erythrocytes. This leads to the release of toxic metabolic products, including oxidant compounds. We measured the serum concentration of the antioxidant, ascorbic acid, in 129 patients presenting with acute falciparum malaria infection and in 65 healthy individuals. None of the study subjects administered any form of ascorbic acid supplementation within one week prior to participation in this study. The mean serum ascorbate concentration in infected adult males (n = 49, age range 18-50 years) was found to be 2.02 +/- 0.20 mg/dL, and it was 2.03 +/- 0.24 mg/dL in infected adult females (n = 56, age range 18-50 years). These values were significantly greater than the serum ascorbate levels (1.54 +/- 0.10 mg/dL) in healthy adult males (n = 28) and females (n = 28) (p < 0.05). In children (age range 3 to 5 years), the serum ascorbate concentration was significantly lower (1.95 +/- 0.20 mg/dL) during infection (n = 25) than in their healthy counterparts (2.9 +/- 0.24 mg/dL, n = 9) (p < 0.05). It is evident therefore that ascorbic acid plays a significant role in the pathogenesis of acute falciparum malaria in adults. Infected children also need to be given supplemental doses of ascorbate in view of the weakness of their immune system.