The size, geographic distribution, and specialty mix of the US physician workforce continue to interest American health policy analysts. Evidence suggests that the United States is on the verge of a serious oversupply of physicians, particularly nongeneralist physicians. Canada faces some of the same problems in physician supply, cost, and distribution as does the United States. Unlike the American states, however, the Canadian provinces, which have responsibility for financing health care, have in recent years made changes in their physician workforce policies that address these problems. Of particular note, Canadian provinces have developed policies that limit medical school enrollments, adjust the specialty training mix to better accord with needs, and establish physician practice location incentives. This article proceeds on the assumption that historical and contemporary similarities between medical care systems in Canada and the United States make comparisons between them potentially valuable. It offers a historical perspective on the evolution of workforce planning in the 2 countries and identifies 3 periods of policy development. It also compares and contrasts the relative size and specialty composition of the Canadian and US workforces and discusses how Canadian initiatives have diverged from American policy. Unless the United States devises its own coordinated workforce strategy, it will have considerable difficulty limiting physician workforce growth and influencing specialization and distribution in the future.