In this lecture, Professor Michel Foucault makes an in-depth study of the problems currently afflicting medical institutions and the medical practice. He deals with the thesis set forth by Ivan Illich in his book Medical Nemesis--The expropriation of Health, as well as the 1942 Beveridge Plan, but goes even further back in history to discover the origin of the medical crisis common throughout the world--back to the XVIII century roots of the social practice of medicine. He also describes the phases through which medical activity has passed from then until now and deals with what he calls the political economy of medicine. Finally, he reaches the conclusion that what matters is not so much the present crisis of medicine, which he considers to be a false concept, but the discipline's historical model dating from the XVIII century and serving to determine to what extent it can be modified.