This paper explores the causal relationship between primary schooling and adult HIV status in Malawi and Uganda, two East African countries with some of the highest HIV infection rates in the world. Using data from the 2010 Malawi Demographic Health Survey and the 2011 Uganda AIDS Indicator Survey, the paper takes advantage of a natural experiment, the implementation of Universal Primary Education policies in the mid 1990s. An instrumented regression discontinuity approach is used to model the relationship between increased primary schooling and adult women's HIV status. Results indicate that a one-year increase in schooling decreases the probability of an adult woman testing positive for HIV by 0.06 (p < 0.01) in Malawi and by 0.03 (p < 0.05) in Uganda. These results are robust to a variety of model specifications. In a series of supplementary analyses a number of potential pathways through which such effects may occur are explored. Findings indicate increased primary schooling positively affects women's literacy and spousal schooling attainment in Malawi and age of marriage and current household wealth in Uganda. However primary schooling has no effect on recent (adult) sexual behavior.