Social insurance was initiated in France on a national scale in 1930 and now covers about 98.5 per cent of the population. The coverage expanded the limits of traditional sickness insurance for curative medicine and had a growing impact on overall health and social policy. French social insurance is a public service run by organizations which retain the voluntary status of the old mutual funds. The social security budget is independent of that of the government, which contributes less than 20 per cent of the overall social budget of the nation. The relationships between the medical profession, private and public hospitals, preventive care organizations, social insurance funds, and central and local governments have become very complex. The huge social security organization has acquired competence in planning and in technical organizational matters and consequently has had a great influence on medical care patterns. Social security adopted the direct payment system in its relationships with the medical profession; therefore the latter has retained its independent status. But, for public and private hospitals, the payment system is indirect. A special branch was created in 1945 to deal with capital investments in hospitals and health institutions concerned with preventive medicine. Social insurance contributed greatly to facilitating access of patients to all kinds of medical care, either public or private, curative or preventive, and helped the government by participating in the construction of a complex network of health institutions for the benefit of the whole population. This task is not yet achieved, and greater coordination and additional resources are necessary. But there is no doubt that social insurance was and still is a powerful factor in the continuing improvement of the nation's health and living conditions.