The Institute of Medicine report entitled Unequal Treatment recommended that all health care professionals receive training in cross-cultural communication-also called "cultural competence"-as one potential strategy for addressing racial or ethnic disparities in health care. Although evidence shows that cultural competence training improves the attitudes, knowledge, and skills of physicians as well as patients' ratings of care, no definitive evidence has yet linked this training to improved health outcomes. Recently, there has been great interest in the field of cultural competence, including an expressed desire for a better understanding of its key principles, of effective ways of engaging clinicians in this area of instruction, and of the link between training and health outcomes. On the basis of years of experience in the field, the authors share key perspectives in all of these areas, with particular focus on a set of guidelines for measuring the impact of cultural competence training on health care outcomes. The authors maintain that cultural competence represents an important building block of clinical care, as well as a skill set that is central to professionalism and quality. Cultural competence training should be evaluated in a stepwise fashion by using the tools of health services research and the principles of quality improvement, and it should be held to the same standards as other educational interventions and activities. Just as medicine strives to meet other challenges in U.S. health care, so should it focus on developing the skills needed to care for the country's diverse population.