Routine monitoring of the efficacy of anti-malarial drugs used is necessary for effective case management, early detection of drug resistance and to provide background information for the development and evaluation of drug policies. In parallel with yearly clinical  monitoring the susceptibility of Plasmodium falciparum to current ACT used in Vietnam, the study aims to investigate the molecular markers (to artemisinin and partner drugs) and using them to support the early detection of drug resistance - one of the actions required in dealing with the emergence and possible spread of P. falciparum resistance.