Self-efficacy theory has had considerable influence in studies of health-related behaviors, including the prevention of sexual transmission of HIV. However, imprecise operationalization of self-efficacy theory in HIV prevention research is common and has important implications for the prediction of risk-reducing behavior from self-efficacy beliefs. In many instances, constructs other than self-efficacy have been assessed. In this article, the operationalization and measurement of self-efficacy in the context of HIV-risk-reduction research are reviewed and challenges inherent to such efforts are identified. Recommendations for enhancing the prediction of risk-reducing behavior from self-efficacy beliefs are also provided.