This paper reports the comparative antimalarial efficacy of intravenous artelinate and artesunate in rats. Prior to efficacy experiments, a Plasmodium berghei-Sprague-Dawley rat model of malaria was developed, in which the clearance effects of intravenous drugs could be readily compared. In efficacy experiments, groups of P. berghei-infected rats were given 3 daily intravenous treatments of artelinate or artesunate at molar equivalent dose rates (total of 0-191.2 micromoles/kg). Artelinate was superior to artesunate in terms of clearance (100% clearance dose of 95.6 micromoles/kg (40 mg/kg) versus 191.2 micromoles/ kg for AS (73.4 mg/kg)) and parasite clearance time (1.7 +/- 0.5 days for AL versus 2.7 +/- 0.5 days for AS at a dose rate of 191.2 micromoles/kg, P < 0.01). No frank clinical toxicity was observed, though both artesunate and artelinate induced dose-related vascular necrosis at the site of injection. The necrosis was less severe and reversible when the drugs were administered via femoral, rather than tail/foot veins. The data suggest that the P. berghei-7-week-old Sprague-Dawley rat model of malaria is reproducible and useful for assessing the efficacy of antimalarials and that artelinate is at least as potent, and safe, as artesunate, the leading clinical treatment for severe malaria.