This study utilizes state-of-the-art PK designs and drug assay methods relying on a combination of intensive and population models to optimize PK/PD analysis. Intensive studies using serial sampling in a relatively small number of subjects will address focused questions on PK exposure while population studies using less frequent sampling in large numbers of subjects will study relationships between PK exposure, clinical response (treatment failure, new infection, and placental malaria), and toxicity (neutropenia) while considering multiple potential covariates. This study includes development and utilization of small volume assay methods for ACT and ART to optimize PK/PD study in children and pregnant women and will be a useful tool for future research trials in resource limited settings.