The trial described here proposes to assess the current recommended doses given in the normal way, and if necessary a higher dose of artesunate. There is no known dose related toxicity with artesunate, and doses up to 10mg/kg/day have been given (by us) without any adverse effects[10]. The two features of this study which differ from normal studies in uncomplicated malaria are the repeated blood sampling and the 7 day in-patient stay. If responses to artesunate are poor it is essential to have characterised the blood concentration profile as well as the parasitological response to differentiate resistance from abnormal pharmacokinetics.