The efficacy and tolerance of artemether administered intramuscularly twice daily (1.6 or 3.2 mg/kg/day) were evaluated in 47 children (mean age 2.4 years old) suffering from mild (n = 28) or severe (n = 19) attacks of Plasmodium falciparum malaria. Tolerance was also investigated in 5 additional children for whom the efficacy could not be assessed, because the parasitaemia was too low on inclusion. Antipyretics were systematically administered and therefore efficacy of the treatment was scored according to the decrease in the density of the parasite and the remission of severe symptoms in those patients with severe attacks. Parasites were eliminated in all patients in a mean of 47.7 +/- 9.8 hours. The time to eradication was not significantly affected by the dose, prior administration of an anti-malarial agents to treat the attack or the severity of the attack. There were two cases of clinical and parasitological regression, on days 14 and 21. There were no deaths. The neurological symptoms of severity resolved in 48 hours in most cases. Local and systemic tolerance was excellent.