(1) Completed a third and final year of follow-up on our cohort study in Thmar Da on the Cambodia-Thailand border. Due to significant loss to follow up (several hundred individuals have moved permanently away from the area) and declining incidence of both falciparum and vivax malaria, we decided to terminate this study in May 2011. We are presently preparing a final spreadsheet, which includes 3 years of follow-up for episodes of falciparum and vivax malaria and five cross-sectional surveys for asymptomatic P. falciparum and P. vivax parasitemia. With this spreadsheet, we will investigate whether hemoglobin E and other RBC polymorphisms influence the incidence of malaria. (2) Performed a final analysis of our case-control study of severe malaria, conducted 2005-2008 in Pursat, Cambodia. (3) Completed a 2-year study of parasite clearance rates in Pursat, Cambodia. (4) Completed a 1-year study of parasite clearance rates in Ratanakiri, Cambodia. (5) Initiated three parasite clearance studies in Pursat, Preah Vihear (new site), and Ratanakiri. We are conducting these studies in collaboration with TRAC the Tracking Artemisinin Resistance Collaboration. This consortium, which Dr. Fairhurst presently co-chairs with Dr. Arjen Dondorp (Mahidol-Oxford Research unit), involves our three sites in Cambodia, as well as additional sites in Cambodia, Thailand, Burma, Laos, Vietnam, India, Bangladesh, Nigeria and Kenya. The purpose of TRAC and our own studies is to (i) map the artemisinin resistance phenotype across Southeast Asia and (ii) to improve our understanding of parasite clearance in response to artesunate. Specifically, we are interested in how hemoglobin E (HbE), naturally-acquired immunity and intrinsic parasite susceptibility to artemisinins influence the parasite clearance curve. Our three sites were chosen for study because while they each have high prevalence of HbE, they differ in levels of acquired immunity and in parasite IC50s to artemisinins and other antimalarial drugs.