Substitution of day-treatment in close connection with community care for inpatient service in a general mental hospital is subject of an experimental research project. Effects of the experimental care condition (the S-condition) are established by means of a clinical trial which refers to a random allotment of 105 patients to the S-condition and 57 patients to the control condition of standard hospitalization. All patients coming from a circumscribed area of 95.000 inhabitants are included, except those admissions for reason of dementia and psychiatric expertise requested by court. Each patient will be followed up for two years. A case register monitors all contacts with mental health facilities. Differential effects of the S-condition will be analyzed on various levels: e.g. the patient with his symptoms and social disabilities; the burden on the relatives; the pattern of care; the intra-organizational changes in the mental hospital; aspects of integration of services and continuity of care; and financial costs and benefits.