There is societal consensus that cancer clinical trial participation is unjust because some sociodemographic groups have been systematically underrepresented. Despite this, neither a definition nor an ethical explication for the justice norm of equity has been clearly articulated in this setting, leading to confusion over its application and goals. Herein we define equity as acknowledging sociodemographic circumstances and apportioning resource and opportunity allocation to eliminate disparities in outcomes, and we explore the issues and tensions this norm generates through practical examples. (...) We assess how equality-based enrollment structures in clinical cancer research have perpetuated historical disparities and what equity-based alternatives are necessary to achieve representativeness and an expansive conception of participatory justice in clinical cancer research. This framework addresses the breadth from normative to applied by defining the justice norm of equity and translating it into practical strategies for addressing participation disparities in clinical cancer research. (shrink)