Dental caries (tooth decay) and periodontal disease are among the more widespread chronic diseases affecting mankind. This volume gives the definition of dental caries and periodontal disease and reviews problems in measurement of these disorders (Chap. 2). Chapter 3 discusses the suitability of these dental problems as indicators of oral health status from the point of view of prevalence, severity, and possible adverse consequences, and it describes their responses to dental care. Chapter 4 presents the RAND Health Insurance Experiment (HIE) definitions of these conditions and describes the methods for measuring their prevalence and adverse impacts. Chapter 5 presents data from the HIE enrollment procedures from all six sites. Finally, proposed quality-of-care criteria for the two diseases, which will be applied in analyses at the end of the experiment, are introduced in Chap. 6 and given in detail in an appendix.