Artemether-lumefantrine is a new fixed antimalarial combination effective against multidrug-resistant falciparum malaria. A prospective electrocardiographic study was conducted in 150 patients receiving artemetherlumefantrine and 50 treated with artesunate-mefloquine. There was no evidence for clinically significant changes in the electrocardiographic intervals and in particular no relationship between plasma concentrations of lumefantrine and QTc prolongation. Artemether-lumefantrine does not have significant cardiac effects at therapeutic doses.