Abstract
The WHO programme on epidemiology of mental disorders started in the early 1960's with a series of reviews of knowledge. These were followed by activities aiming at four main goals: the standardization of psychiatric diagnosis, classification and statistics; the development of standardized internationally applicable instruments for the assessment of mental patients and of variables relevant to the assessment of mental illness; the conduct of epidemiological studies of mental disorders; and the training relevant to the above goals. The paper provides a description of the activities undertaken to achieve these goals and stresses the importance and usefulness of the collaboration of individuals, experts and institutions all over the world in this effort.