This Perspective addresses the need for an integrated system of formative and summative assessment in undergraduate medical education with a focus on the formative. While acknowledging the importance of summative assessment, which asks whether trainees have met criteria for progression, the authors propose that a formatively focused assessment system can best accomplish a central task of competency-based medical education: transmitting feedback to learners in a format and a manner that will help them to improve, develop, and grow. Formative assessment should not be seen as a set of singular events but, rather, as a process that is organized and integrated over time, much like the cycle of quality improvement in medicine. To justify this position, the authors discuss its conceptual underpinnings and rationale, including the need to prepare learners for the formatively focused assessment system of graduate medical education. Next, the authors identify assessment strategies that could be employed, as well as the characteristics of an institutional culture and the learner–teacher relationship necessary for a learner-centered, improvement-focused assessment system to succeed. Finally, an infrastructure for such a system is proposed. This consists of a foundation of well-articulated and disseminated milestones for achievement and four pillars: faculty development, learner development, longitudinal academic advising and coaching, and documentation of developing competence. The authors conclude by suggesting that the guidelines proposed are analogous to the principles of continuity and coordination of care, so much valued in the world of medicine yet often overlooked in the world of education.