Despite documented high cure rates of ACT in Tanzania, and Africa elsewhere, clinical trials conducted in Tanzania with Swedish International Development cooperation Agency (SIDA) and Swedish Research Council support, provide evidence for in vivo selection of lumefantrine tolerant/resistant parasites among recurrent infections. Similarly, molecular epidemiology studies from Bagamoyo District, Tanzania, have shown temporal selection of lumefantrine associated genetic tolerance/resistance markers in the parasite population following wide scale use of Artemether-lumefantrine, but without signs of compromised treatment efficacy.