The extensive use of diagnostic tests and the accelerated development of new diagnostic technologies have become major concerns and important factors in escalating health care costs. Not only are diagnostic services themselves expensive, but there is a close link between diagnostic testing and the utilization of therapeutic services. High levels of diagnostic test utilization have been associated with a concomitant high use of surgical and interventional treatments (1). Of course, high utilization may simply reflect early and appropriate detection of and its management. To the extent, however, that diagnostic tests may be inaccurate or demonstrate levels of disease that do not require treatment, high testing rates may lead to a cascade of medical interventions that will not, in the long run, improve health outcomes (2). An important component, therefore, of quality of care enhancement and rational cost control in medicine may well be the cost-effective and appropriate use of diagnostic services. As the importance of diagnostic tests and procedures and their relationship to medical care resources become better recognized, there will be even more interest in economic evaluations, which start with and focus on diagnostic testing. This will create opportunities for new insights into the reasons for the high cost of medical care and will undoubtedly uncover ways to improve quality rationally and decrease waste and unnecessary expenditures. The SETTING PRIORITIES FOR DIAGNOSTIC TECHNOLOGY ASSESSMENT AND COSTEFFECTIVENESS ANALYSIS