Objective: In recent years there has been a growing awareness of the prevalence of sexual violence in U.K. university student populations, yet prevention efforts are in their infancy. Evidence from the United States shows that empowering bystanders to intervene to prevent violence rather than focusing on perpetrators or victims is a promising strategy particularly suited to university settings. Public Health England commissioned a bystander program, The Intervention Initiative, for U.K. universities. This paper discusses the theoretical underpinnings of the bystander approach and the challenges for practical implementation in Europe. Method: We review findings from research relating to bystander theories, social norms theory, and effective prevention programming that inform the development of maximally effective bystander programs. Results: Bystander programs are complex, multifaceted interventions based on taking participants through the different stages required for an individual to move from inaction to action as described by Latané and Darley, 1969, 1970 in their organizing framework for bystander intervention and incorporating a social norms element. Programs that adhere to the principles for effective prevention as set out by Nation et al. (2003) are most likely to be effective. We demonstrate how these criteria informed the cultural specificity of The Intervention Initiative to U.K. university settings and the challenges in adapting the approach for European settings. Conclusion: More research is needed to develop and test bystander programs in different European countries to build an evidence base for effective prevention programming. (PsycINFO Database Record (c) 2017 APA, all rights reserved)