In a rat model of Pneumocystis carinii pneumonia, a 3-week infusion of deferoxamine producing concentrations in plasma of greater than or equal to 1.5 mu g ml(-1) eliminated the trophozoite life cycle stage. Since this concentration is well below that routinely achieved in patients treated for iron overload, deferoxamine has promise as a therapy for AIDS-associated P. carinii pneumonia.