Research suggests that the much higher HIV prevalence among young women in sub-Saharan Africa than among males of their age cohort is linked to the high prevalence of age-disparate sexual partnerships, and that incorrect beliefs about the relationship between age and HIV-risk are partly responsible. ideas42 report the results of an experiment that tests whether a simple, computer-based “HIV risk game” leads to better understanding of the relationship between HIV-risk and age among low-income South African adolescents than a version of the traditional “brochure approach” to dispensing information does. Our results are striking. The randomly assigned treatment group, which receives repeated doses of information about the link between age and HIV-risk as feedback to their own responses to simple questions about relative HIV-risk, is significantly more likely to correctly identify which of a pair of hypothetical men or women of different ages is more likely to have HIV than the control group. Subjects in the treatment group answer, on average, 1.65 times as many questions about HIV risk and age correctly as those in the control group. ideas42 also find that subjects’ (particularly female subjects’) beliefs about HIV risk among women are less accurate than their beliefs about HIV risk among men. Finally, a follow-up survey with no significant difference in attrition rates between those in the treatment and control groups, shows substantially higher information retention among treatment subjects than among control subjects.