Highly skilled primary care is a hallmark of high-performing health care systems. We examine nurse practitioners' role in delivering primary care and the effects of current restrictions on their ability to practice. By resolving differences between states' individual scope-of-practice regulations, we can fully benefit from the skills of advanced-practice nurses in all fifty states. We recommend substantive changes in the way health care professionals in all disciplines are trained, and in their roles, so that patients can receive appropriate and cost-effective care from skilled and fully functional health care teams.