1. All authors are with the Accreditation Council for Graduate Medical Education. Eric S. Holmboe, MD, FACP, FRCP, is Senior Vice President, Milestone Development and Evaluation; Kenji Yamazaki, PhD, is Outcome Assessment Project Associate; Laura Edgar, EdD, CAE, is Executive Director, Milestones Development; Lisa Conforti, MPH, is Research Associate for Milestones Evaluation; Nicholas Yaghmour, MPP