We study externalities and complementarities of three HIV/AIDS prevention interventions:
HIV/AIDS education, easy access to male circumcision, and education support for girls. The
study is based on a sample of 7,971 students in 33 secondary schools near Lilongwe, Malawi and
we focus on the behavior within the existing 124 classes in these schools. In order to understand
the potential externalities of the decision to get circumcised we randomize the fraction of students
within classrooms who get offered this treatment (0%, 50% and 100%). We find evidence of
peer effects given that untreated students in 50% Treatment classrooms were 3.8 percentage
points (79%) more likely to get circumcised than students in No Treatment classrooms. We also
provide evidence of important reinforcement effects in take-up when male circumcision is offered
among close friends. Our research design to study the complementarities of these interventions
is based on the randomized allocation of the different mix of interventions across classrooms.
We find limited evidence of complementarities among the three interventions.