The feasibility of day-treatment for the severily mentally ill was tested by means of a randomized experiment.

Study-design: Longitudinal randomized experiment with blocked allotment in a ration 9 experimentals to 5 controls; follow-up period of 2 years.

Patients: 103 in the experimental condition; 56 in the control condition; the cohort is representative for psychiatric patients admitted to Dutch psychiatric hospitals.

Inclusions: Patients accepted for admission to a psychiatric hospital, living in a circumscribed catchment-area.

Exclusions: Patients suffering from dementia and those assessed on request of court were the only exclusions from the study.

Conditions: The control condition consists of standard clinical care; the experimental condition consists of a newly developed day-treatment program.

Inferences: Day-treatment is not feasible for some 40% of this severely ill population; 38% can be treated in a day-program in a satisfactory degree. Time series are presented that indicate which percentage of patients can be taken at which point in time into day-treatment.

The authors quest the monopoly of clinical care for the severely mentally ill in the Dutch mental health system. They claim that their results are an empirical contribution to a rational re-evaluation of this monopoly.