This grant will study the acquisition of drug resistance by malarial parasites. Resistance to antimalarial drugs is correlated with genetic changes in malarial enzymes called DHPS and DHFR (dihydropteroate synthase and dihydrofolate reductase). Malarial parasites resistant to these drugs carry alleles of DHPS and DHFR that contain point mutations reducing binding of drug to enzyme. Therefore, the goal of the project is to compare the rates of change in parasite alleles known to be associated with drug resistance, to identify selective forces that influence the rate of selection of drug resistance in Kenya. Subsequently, this information will influence public health decisions in treatment protocols for malaria in East Africa.