Intensive efforts are under way to improve health care quality and safety throughout the United States and abroad. Many of these efforts use the quality improvement collaborative method, an approach emphasizing collaborative learning and exchange of insights and support among a set of health care organizations. Unfortunately, the widespread acceptance and reliance on this approach are based not on solid evidence but on shared beliefs and anecdotal affirmations that may overstate the actual effectiveness of the method. More effective use of the collaborative method will require a commitment by users, researchers, and other stakeholders to rigorous, objective evaluation and the creation of a valid, useful knowledge and evidence base. Development of this evidence base will require improved conceptions of the nature of quality problems, quality improvement processes, and the types of research needed to elucidate these processes. Researchers, journal editors, and funding agencies must also cooperate to ensure that published evaluations are relevant, comprehensive, and cumulative.