Staffing patterns are a major concern in the planning and administration of psychiatric facilities. The cost of professional and sub-professional personnel are the largest expense on psychiatric institution operating budgets. Trained professionals are in short supply and for the foreseeable future will not be available in adequate numbers to staff existing and developing programmes. Such considerations make important the development of more efficient methods for deciding upon staffing levels. At present, clinical experience and uncontrolled comparison of differently staffed clinical programmes are the usual justifications for improved staffing. This study was undertaken to investigate whether a relationship existed between staff time spent in treatment of patients and outcome for a patient group.