This randomized, non-comparative clinical trial without placebo was carried out to assess the efficacy and tolerance of artesunate for treatment of acute Plasmodium ovale malarial attacks. Thirty Cameroonese patients were included. All presented acute Plasmodium ovale malarial attacks with parasitemia in excess of 500 asexual forms per mm3. Four days after treatment with artesunate, all 30 patients were asymptomatic with no parasitemia. Reduction rates were 93.9 p. 100 for asexual forms and 75.4 p. 100 for gametocytes. Parasite clearance was achieved within 38.8 hours and fever disappeared within 36.6 hours. Tolerance was excellent in 29 patients. The remaining patient briefly complained of mild vertigo. A transient decrease in reticulocyte levels was observed in one patient initially presenting anemia. Artesunate appears to achieve rapid and complete resolution of acute Plasmodium ovale malarial attacks. Since artesunate eliminates both asexual forms and gametocytes, it also acts on transmission by limiting the duration of survival of asexual forms.