A traveler returns with cyclical fever — falciparum malaria; artemether-lumefantrine is given. ACT (artemisinin combination therapy) clears falciparum fast — artemisinin kills parasites rapidly, lumefantrine mops up; 3-day course, complete it. Severe malaria (cerebral, high parasitemia) needs IV artesunate — the mortality difference is proven. Vivax/ovale need primaquine for 14 days to kill dormant liver hypnozoites — but G6PD deficiency turns primaquine hemolytic, so test first. Species decides the regimen — the smear is the prescription.