This thesis defines the general nature of health care services and examines some issues of medical practice controlled by the state which are related to an individual right to health care. Occupational control of health care professionals, especially doctors, is the main focus of this thesis. Their legal liabilities are discussed, as well as medical licensure, from a compar tive perspective that examines differences in health care systems between Canada and Japan. First, a general framework for the scheme of medical practice control is established. Chapter 1 discusses rationales for controlling medical practice with reference to the quality of health care, as well as to the justifiability and efficiency of the health care system. It also analyses sociological aspects as background to legal control and to the actual functions of the controlling scheme. The influence of public health insurance on medical practice is discussed, as well as its inherent problems. Chapter 2 discusses select issues in the control of medical practice. The first is the licensing of doctors and other health care professionals. The definition of medical practice is thoroughly examined. In addition, the different perspectives in judicial processes are made clear by reference to a case in Japan. The legal duties of doctors are discussed as involving quality assurance through judicial process and legal precedents. It compares the strategies of Canada and Japan in terms of constructing the duties, which reflect the differences between common-law countries (Canada) and civil-law countries (Japan), as well as differences of culture between the two countries.