The study was conducted at Siaya District Hospital, in Nyanza Province, Kenya. Non-pregnant adults who provided consent to participate, who were found to have pure Plasmodium falciparum malaria parasitemia with at least 500 asexual parasites per microliter, and who agreed to undergo HIV counseling and testing were eligible for participation. Clients were then followed with repeat physical examinations and blood smears on day 1,2,3,4,7,14,21 and 28 and any non-scheduled day when they were sick. Those that failed therapy were treated with quinine to clear parasitemia. Samples were also taken to measure reinfection vs. recrudescence, pharmacokinetics, and antifolate resistance markers.