This paper aims to clarify the concepts and terminology of clinical research, evaluation, and quality. Clinical research or clinical epidemiology aims to demonstrate the efficacy of medical care. The optimal methodology is a randomized, double-blind trial that allows a causal inference in respect of efficacy. This should be the first stage before generalization of all medical practice. Evaluation of quality of care aims to verify the effectiveness of medical care by comparing practice with references. The optimal methodology is clinical audit that allows fine-tuned diagnosis of the existence of deviant practices. The analysis of causes and correction of the care process are an integral part of the evaluation work. Thus quality assurance and quality management concepts and methods have been developed which tend to ensure solutions for better care and to maintain the level of quality of care to achieve patient satisfaction. Evaluation, clinical research and management quality could in fact be seen as the complementary facets of a comprehensive approach to quality of care.