Consumers, payers, and policymakers are demanding to know more about the quality of the services they are purchasing or might potentially purchase. The information provided, however, is often driven by data availability rather than by epidemiologic and clinical considerations. This report presents an approach for selecting medical conditions for measuring technical quality of care, based on the expected impact of improved quality of care. The authors use this model to select measures that could be used to inform purchasers and consumers about the quality of care delivered by different health plans. For the major causes of mortality and morbidity (i.e., limited-activity days) in the United States, it estimates the expected impact of improved care using information on the prevalence of disease, the efficacy of available treatments, and the current quality of care being provided.