SummaryThis paper is a review (if the methods used in assessing the quality of medical care. In accordance with a previous classification scheme, five main groups of quality evaluation studies are examined, and current problems in evaluation are pointed out. The studies of the structure of care raise three problems: organizational features are possibly linked to mortality rates, cost-effective quality assurance settings remain to be selected, and the relationship between the physician performance and the quality of care is questionable. The studies of the process of care raise vexing issues of validity: auditing and peer review might lead to a deadly sameness, or might represent only attempts in containing utilization. There are stronger grounds for studying the outcomes of care. However, such studies are often limited to the medical aspects of outcomes. Gross measures of mortality are criticized: they are either valid, nor reliable measures of the quality of care. The studies combining process and outcome measures, e.g.«tracers», and the studies of strategies of care, e.g. decision-analysis-like audits, could provide strong foundations for quality assessment. There is a need for studying humanitarian aspects of care, that is, the art of care, and for developing patient-oriented measures of care, such as quality of life or satisfaction scales. The formulation of diseasespecific risks and prognoses could be a first step towards a common language between the physician and his patient.