 Resistance of Plasmodium falciparum to anti-malarial drugs is a serious impediment to the control of malaria. In order to facilitate formulation of effective regional drug policies and to provide a database for decision-making on the implementation of combination therapy CAT, it is essential that the in vivo response to CAT be investigated. In the South East African Combination Anti-malarial Therapy SEACAT evaluation, there is a comprehensive evaluation of the phased introduction of combination anti-malarial therapy in Mozambique. As a component of this evaluation, in selected Mozambique sites where intensity of malaria transmission is high, a direct parallel group comparison of monotherapy SP with CAT artesunate plus SP will be conducted according to this protocol. 