Background Plasmodium falciparum causes malaria and approximately 665 000 deaths each year. Previously chloroquine (CQ) and sulphadoxine-pyrimethamine were the principle drugs for the treatment of malaria. Due to widespread resistance to these drugs1, the World Health Organization recommends that P. falciparum in Africa should be treated with artemisinin + amodiaquine, artemether + lumefantrine (AL) or dihydroartemisinin + piperaquine2 (DP). However, resistance to artemisinins appears to be developing3,4, resistance to amodiaquine exists2 and treatment with AL rapidly selects for parasites with increased tolerance (5 times higher inhibitory concentration) to lumefantrine5-7.