Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS)-related knowledge and behaviors were assessed in face-to-face structured interviews with 314 Ethiopian military personnel. A significant finding of this research was the association between HIV/AIDS knowledge and risky sexual behavior. That is, military personnel who had inaccurate knowledge about HIV/AIDS transmission and prevention were 3.4 times as likely to engage in combined sexual risk behaviors compared with personnel with accurate knowledge, after controlling for age, military rank, and marital status (odds ratio, 3.4; 95% confidence interval, 1.86-6.22). This finding highlights the potential value of educational programs in slowing the spread of HIV/AIDS in sub-Saharan Africa.