SYNOPSISSocial psychiatry, like social medicine of which it is a part, has two basic sciences – biology and sociology. People with psychiatric disorders suffer from acute breakdowns or chronic impairments which can be severely disabling in themselves, but these are often precipitated, amplified or maintained by social pressures and social disadvantages and by personal reactions, such as a loss of self-esteem and self-confidence. It is impossible, therefore, to draw a line between the medical and the social aspects of treatment, care and prevention.The chief innovations during the past 40 years have been made in the context of a change-over from a system of care based on large institutions towards a more open but much looser and less-coordinated system of smaller units managed by staff from different professions who have developed their own, sometimes conflicting, views as to the best ways of helping the mentally disabled. Nevertheless, knowledge has accumulated which, if properly applied, could lead to a better quality of life for the ill and disabled and a decrease in the burden placed upon relatives. Further innovations are now required which will lead to the development of a responsible, comprehensive and integrated mental health service.It is not yet known whether social measures taken to relieve or prevent lesser psychiatric disorders will lead to a decrease in the incidence or prevalence of more severe conditions and this question deserves further investigation. There is evidence, however, that relatively inexpensive help can be useful in the short term.Progress will depend upon the accumulation of new knowledge. One of the most encouraging trends has been the improvement of evaluative designs and methods aimed at testing ideas for improving services, thus allowing planners to make better informed decisions.