In recent years, methods have been developed to evaluate effectiveness, cost-effectiveness, and quality of oral health services and delivery mechanisms. These evaluation techniques are important to the application of oral health services, because most oral health services have not been adequately evaluated. For many services, evaluation may not be necessary. However, there is wide variation in clinical practices and accumulating evidence that many health practices, although based on reasonable pathophysiologic grounds, are not resulting in their expected health benefits. This has led to the suggestion that all clinical precepts may be questioned. A number of measures are used by researchers to evaluate the quality and effectiveness of oral health services. These include: Effectiveness and appropriateness: Methods available to assess health practices range from clinical observation to strictly controlled randomized clinical trials. Cost-effectiveness: Benefit-cost and cost effectiveness analyses. Quality: No tool exists that will single-handedly measure quality. Current methodologies should be based on the following three-dimensional conceptual framework: Structure (evaluation of facilities, equipment, personnel, and organization to deliver care), process (observance of the patient-provider interaction), and outcome (measures of health status and patient outcomes). Little to no information on the quality and effectiveness of oral health delivery systems is available in the United States; the most common system in place is solo, private, fee-for-service practice. Specific questions, conditions, or practices that need evaluation include: Alternative frequencies of oral prophylaxis; Use of fluoride and other remineralization techniques for early decay; Alternative methods to replace missing teeth, including the appropriateness of dental implants; Methods to prevent and treat symptoms of dry mouth; Treatment of the medically compromised patient; Prevention of oral complications of cancer treatment; Appropriateness of new and existing diagnostic technologies; Diagnosis and treatment of oral cancer; and Alternative oral health delivery systems, financing, and expanded responsibilities for allied health professionals.