The efficacy of artemether (a qinghaosu derivative) administered intramuscularly for the treatment of Plasmodium falciparum malaria was compared to quinine in an open randomized trial including 54 patients in eastern Sudan, where chloroquine resistance is common. The artemether treatment (5 d intramuscular regimen) was effective and the drug was well tolerated. All patients had cleared the parasitaemia and were free of symptoms 48 h after initiation of treatment. The parasite clearance time was comparable in patients receiving artemether and quinine. No side effect was reported by patients receiving artemether. No recrudescence was seen in 21 patients treated with artemether who completed 28 d follow-up. In the quinine group 3 of 18 patients had recrudescences, or possibly reinfections, on days 14, 21 and 28.