<qa>  What is the resistance of Plasmodium falciparum to anti-malarialThe resistance of Plasmodium falciparum to anti-malarial drugs is a serious impediment to the control of malaria. In the South East African Combination Anti-malarial Therapy SEACAT evaluation, there will be a comprehensive evaluation of phased introduction of combination anti-malarials CAT in Mozambique, Swaziland and South Africa. In order to facilitate formulation of an effective regional drug policy and provide a database for decision-making on the implementation of combination therapy, it is essential that the in vivo response to CAT in all three countries be investigated. An SP therapeutic efficacy study will be conducted according to this modified WHO protocol to guide the selection of CAT. After CAT is introduced an in vivo CAT efficacy study will then be conducted to evaluate the efficacy of artesunate plus SP or artemether-lumefantrine in KwaZulu Natal and Limpopo. In areas of low intensity malaria transmission the CAT in vivo study results will be compared across sites and with those found at baseline with monotherapy, for each site. 