Objectives To study the efficacy of orally administered dihydroartemisinin, a derivative of artemisinin, in the treatment of malaria. Methods Thirty-seven patients with malaria were treated with dihydroartemisinin in Beijing and in Ruili City, Yunnan Province. 25 cases had falciparum malaria with a mean parasitemia of 73218/μl and 12 vivax malaria with a mean parasitemia of 4950/μl. The dosage of the drug was 60 mg daily or 2 mg/kg for paediatric patients for 7 days with the first dose doubled. Results All patients in the study were clinically cured from malaria. Fever subsided 22-72 hours after treatment in patients with falciparum malaria. Their mean fever clearance time was 36.24± 15.30 hours and the mean parasite clearance time 24-72 hours （44.80± 19.09 hours）. One patient had recrudescence 19 days after the disappearance of parasites. Hence the recrudescence rate in falciparum malaria patients was 4.8％. Five patients with early cerebral involvement also completely recovered after treatment. 12 patients with vivax malaria were also cured after the treatment, except one who had relapse 35 days after the treat ment. This patient was cured after another course of combined treatment of dihydroartemisinin and primaquine. All the patients were tolerated the oral administration of dihydroartemisinin and no significant side effects were reported. Conclusion Dihydroartemisinin is effective in the treatment of patients with falciparum and vivax malaria including those with chloroquine-resistant falciparum malaria.