Plasmodium falciparum causes malaria and approximately 665 000 deaths each year. chloroquine and sulphadoxine-pyrimethamine resistant P. falciparum are widespread. An artemisinin derivative combined with lumefantrine, amodiaquine or piperaquine is therefore recommended for the treatment of malaria in Africa. However, artemisinin resistance appears to be developing and resistance/tolerance to amodiaquine and lumefantrine exists. We are presently conducting a study in Guinea-Bissau. Preliminary data indicates that the effectiveness and availability of artemether-lumefantrine (AL), the 1st line drug, is poor. Consequently there is a need for another treatment option. Dihydroartemisinin-piperaquine (DP) has been shown to be efficacious and well tolerated in several African countries and is therefore such an option. A clinical trial comparing the safety and efficacy of artemether-lumefantrine and dihydroartemisinin-piperaquine is therefore needed.