This document is about a study that examined the relationship between various physician characteristics, such as sex, board certification, medical school, malpractice claims, and disciplinary actions, and their performance on a broad range of quality measures for a large sample of physicians in Massachusetts. The study found that few physician characteristics were consistently associated with higher quality of care, and the observed associations were small in magnitude. The authors conclude that publicly available characteristics of individual physicians are poor proxies for performance on clinical quality measures, and that external quality information would be more valuable for patients when choosing a provider.