A precondition for the discharge from an institution of the chronically disabled mentally ill is the availability of adequate alternative facilities and services, optimally meeting their social and mental health needs and allowing as much quality of life as possible at the lowest possible cost. Only a few studies have found alternative care to lead to better outcomes than treatment in good-quality hospitals with respect to illness course and social disablement. Therefore, it is an important question whether extramural care and of what type is better and possibly less expensive than traditional inpatient treatment and for which patients. Health data collected at the national and regional levels provide a basis for continuous monitoring of utilization of services. Such data, however, usually have the limitation of being aggregate in nature and not including contacts with social services. These deficits can be avoided by using cumulative case registers, recording if possible all contacts of the socially disabled mentally ill with intramural and extramural mental health and social services and covering a define catchment area. Because the disabled mentally ill, depending on their own resources and those of their family and the community at large, have basic needs differing in each individual case, as well as various specific needs determined by the illness which they cannot meet on their own, it is necessary to provide a variety of facilities and services and to coordinate their work. Evaluation and cost-effectiveness investigations of complex packages of care yield generalizable results only if the forms of care under study are defined precisely enough.(ABSTRACT TRUNCATED AT 250 WORDS)