This dissertation contains three essays on development economics in the areas of education and health in developing countries. The first chapter evaluates the impacts of girls' education support program on human capital development of 3,997 female students (9th ~ 11th grades) at 33 secondary schools located outside Lilongwe, Malawi. We find that female students treated with one-year tuition and monthly cash stipends are more likely to attend school and have better test scores. We also find that cognitive ability in the treatment group increases by 0.215 standard deviations, and those treated also display higher aspirations for educational achievement. Moreover, there is a significant improvement in time preference (increased patience). In the second chapter, written jointly with Cristian Pop-Eleches and Hyuncheol Bryant Kim, we address two questions: 1) How to promote demand for male circumcision and 2) What is the role of peer effects in demand for male circumcision. We randomly provided free male circumcision and transportation voucher to male students in 124 classrooms across 33 secondary schools near Lilongwe, Malawi. Using a two-step randomized design, we first assigned classrooms into three groups (100% Treatment, 50% Treatment, or No Treatment classrooms) and then also randomly selected half of male students in 50% Treatment classrooms for treatment. We find that our intervention substantially increased the demand for male circumcision by on average 14.2 percentage points (243%). We also find evidence of peer effects since untreated students in 50% Treatment classrooms were 3.8 percentage points (79%) more likely to get circumcised than students in No Treatment classrooms. Finally, we provide evidence of important reinforcement effects when close friends within the same classroom receive the intervention together. The third chapter, written jointly with Cristian Pop-Eleches and Hyuncheol Bryant Kim, explores complementarities of three HIV/AIDS prevention interventions: HIV/AIDS Education, Male Circumcision for boys, and Girls' Education Support aimed at keeping girls in school. The study is based in 33 secondary schools near Lilongwe, Malawi and we focus on the behaviors within the existing 124 classrooms in these schools. Our research design to study the complementarities of these interventions is based on the randomized allocation of the different mix of interventions across classrooms. Our preliminary results indicate limited evidence of complementarities among the three interventions.