Several of the world's accreditation systems for continuing professional development (CPD) are evolving to encourage continuous improvement in the competence and performance of health care providers and in the organizations in which they provide patient care. Clinicians learn best when they can to choose from a diverse array of activities and formats that are relevant and meet their needs. Since choice and diversity are key to meeting clinicians' needs, several CPD accreditors have been engaging in deliberate, concerted efforts to identify a core set of principles that can serve as the basis for determining substantive equivalency between CPD accreditation systems. Substantive equivalency is intended to support the mobility of learners, allowing them to access accredited learning activities that are recognized by various CPD accreditation systems in a manner that maximizes the value of those accreditation systems, while minimizing the burden of adhering to their requirements. In this article, we propose a set of core principles that all CPD accreditation systems must express as the basis for determining substantive equivalency between CPD accreditation systems. The article will illustrate how five CPD accreditation systems (two in the USA, two in Canada, and one in Qatar), differing in focus (activity-based versus provider-based), context, and culture, express these values and metrics, and concludes by identifying the value of substantive equivalency for learners, medical regulators, and CPD accreditation systems.