This report is one of five volumes providing detailed information on the QA Tools, RAND's comprehensive, clinically based system for assessing quality of care for children and adults. The QA Tools indicators encompass screening, diagnosis, treatment, and follow-up in 46 clinical areas and cover a variety of modes of providing care, including history, physical examination, laboratory study, medication, and other interventions and contacts. Development of each indicator was based on the ratings of a panel of experts in the relevant fields and on a focused review of the scientific literature, which is clearly documented for each clinical condition.