Resistance of Plasmodium falciparum to current antimalarial drugs and the continuing development of resistance to new antimalarial formulations is one of the major obstacles to effective malaria control and case management. Parasite populations are highly resistant to chloroquine on an almost worldwide basis (Central America and Haiti being the exceptions) and resistance to the next line of treatment, SP, is widespread in Asia and large parts of East Africa and South America. SP is also now recommended for use as intermittent preventative treatment (IPT) in pregnancy, which adds to concerns about the development and spread of SP resistance. More expensive combination drug therapy using artesunate and other antimalarials in combination is increasingly being recommended in an effort to extend the useful life of drugs and to slow the spread of antimalarial drug resistance. In all likelihood, resistance will eventually emerge for any new single drug or combination formulation that we deploy in the field.