The right to health care is a social achievement of democratic states based on law. In order for this to become effective in a just way, it is necessary for many elements to come together. This article analyses these elements in their different moments: the state as a guarantor of this right and to limit assistance; the health institutions, direct managers of care, which must combine efficiency and equity; and, finally, the health professionals, who are in the final instance the real distributors of resources. Traditionally medicine always omitted evaluation of the socio-economic factors from its sphere. It even came to consider that these questions were opposed to good medical practice. Today such an assertion is unsustainable. For a health professional the path to efficiency passes by way of assuring clinical effectiveness, in this way guaranteeing both the patient's interest and the suitable distribution of resources.