Studies at the individual level have shown a negative effect of education and intelligence on risky behavior. The same has been demonstrated for risky sexual behavior and for HIV-infection rates in sub-Saharan Africa. In path analyses at the country data level, cognitive abilities (seen as depending on education) show a strong negative effect on HIV-infection rates, whereas gross domestic product and modernization each has a small positive effect. A higher proportion of Muslims in the population reduces the HIV-infection rate. Explanations for the effect of intelligence include a better understanding of causal relationships between one's behavior and health, greater awareness of future consequences, indirect intelligence effects, a general rationality effect, a civic embeddedness effect, and more competent management of the problem by governments, e.g. through public education programs about HIV transmission and AIDS. (Contains 1 table and 8 figures.)