The concept of core elements was developed to denote characteristics of an intervention, such as activities or delivery methods, presumed to be responsible for the efficacy of evidence-based behavioral interventions (EBIs) for HIV/AIDS prevention. This paper describes the development of a taxonomy of core elements based on a literature review of theoretical approaches and characteristics of EBIs. Sixty-one categories of core elements were identified from the literature and grouped into three distinct domains: implementation, content and pedagogy. The taxonomy was tested by categorizing core elements from 20 HIV prevention EBIs disseminated by Centers for Disease Control and Prevention. Results indicated that core elements represented all three domains but several were difficult to operationalize due to vague language or the inclusion of numerous activities or constructs. A process is proposed to describe core elements in a method that overcomes some of these challenges. The taxonomy of core elements can be used to identify core elements of EBIs, strengthen the translation of EBIs from research to practice and guide future research seeking to identify essential core elements in prevention interventions.