In this article the development of a rating scale for assessing the level of functioning of psychiatric inpatients is described. The criteria specifying the contents to be covered by the scale were determined by a process which involved the pooling of the specific goals of each of the treatment programs of the psychiatric hospital at Santpoort. The criteria derived from this pool all represent specific aspects of the general concept of `level of functioning' and can be divided into four main categories: activities of daily living, social functioning, physical health, and psychological functioning.

This set of criteria was then used as a device for selecting existing scales from the literature. Since no single scale was found covering the whole range of criteria, a new scale had to be developed, mainly by combining the most suitable (parts) of several rating scales. The new scale was tested upon a sample (N = 549) of psychiatric inpatients from all treatment programs, including chronic patients, patients from short term and rehabilitation programs and patients from a psychotherapeutic community setting.