This Note presents speculation on how the medical community might determine whether more medical care is better medical care by collecting information about the indications and outcomes of medical procedures and services. In particular, it aims to motivate the private practitioner, medical educator, and clinical researcher to search more forcefully and more diligently for the clinical knowledge that seems to be missing today in making policies affecting the distribution and use of medical care. Many current proposals for rationalizing the use of medical care, or for stemming the nation's outlays for such care, derive chiefly from an economic model. There remains a need to clarify the medical dimension of rational and equitable use of services. The authors argue that the generic issue to be explored first is how to identify specific areas where the use of medical services could be reduced without impairing access or quality of care. Major research objectives include (1) determining, from a clinical perspective, whether geographic differences in the use of a number of common medical services represent overuse or underuse (or both, or neither); (2) establishing scientific bases for modifying the delivery of medical care in ways that do not jeopardize or only minimally affect patients' health; (3) developing an economically feasible method, acceptable to physicians, to examine the appropriateness of utilization of services; and (4) identifying specific clinical areas in which future research would be most likely to yield useful findings.