Research aimed at promoting quality of medical care must be quality research. This paper addresses issues of study design that can affect the validity of such research. The authors draw on previous research about medical errors—recognizing that issues of study design pertaining to medical errors apply to other research on quality of care and, indeed, to clinical research in general. The November 2000 Special Issue of Academic Emergency Medicine addressed medical errors in emergency medicine. In that issue, Kyriacou and Coben described three categories of research on medical errors: 1) research aimed at describing the magnitude of the problem; 2) research identifying causal factors for medical errors; and 3) research evaluating interventions aimed at improving quality of care. These three categories correspond to research methodologies that are, respectively, 1) descriptive; 2) qualitative; and 3) analytic. This article discusses challenges to the validity of each type of research and suggests some possible solutions to these problems. In addition, the article reviews projects that illustrate important issues in research quality. Three research projects are discussed: 1) a published project evaluating an intervention aimed at improving quality; 2) a quality improvement project that is transformed into a research project; and 3) a quality monitoring research project that exemplifies how a statistical technique borrowed from industry can offer a unique solution to quality challenges in medicine. Each of these projects demonstrates some of the challenges in researching quality and their solutions.