A major challenge for future health care is the care for dementia patients and their informal caregivers. In usual care, the problems of caregivers often remain invisible until a crisis occurs. This inhibition is partly the result of informal caregivers paying scant attention to their own problems. Another reason is that professionals may not know how to support informal caregivers pro-actively (Van Hout et al., 2000). Therefore the family support programme (Bengtson, 1985: Vernooij et al., 2000) has been transformed into a Systematic Care Programme (SCP-Dementia). The reasons for choosing and studying the efficiency of this programme are the potential to diagnose and treat problems systematically, to cover a wide range of individual problems, its flexibility in connecting interventions to these problems, its suitability for pro-activity and the positive effects of the programme found in our previous study (Vernooij et al., 2000). To study its efficiency a cluster randomised controlled trial design will be used. Randomisation will take place in each of three participating regions. Professionals in the ambulatory mental health care services (psychologists and social psychiatric nurses) will be randomly assigned to either the intervention group or the control group before the recruitment of patients and informal caregivers. The study population consists of pairs of patients and their informal caregivers visiting the ambulatory mental health care service for the first time. The intervention is the training in SCP-Dementia and its subsequent use. SCP-Dementia consists of an assessment of the caregiver's sense of competence and suggestions on how to deal with deficiencies in competence. The follow-up period is one year. The primary outcome is patients´ admissions to nursing homes or residential homes. The secondary outcome is quality of life. Caregivers´ quality of life is assessed by sense of competence (SCQ), depression (CES-D) and physical quality of life (EuroQol). Patients´ quality of life by behavioral problems is assessed by the NPI-Q and the QOL-AD-Scale. The difference in proposed effect was based on previous research in which 14% of the patients in the intervention group and 28% in the control group were institutionalized (Vernooij-Dassen, 1993;1995). To detect a 50% reduction in institutionalization rates with 80% power at the two sided significance level of 0.05, 132 patient-caregiver dyads would be needed for each of the intervention and control arm. We inflated this sample size by a design effect of 1.15 to 152 dyads per trial arm to allow for correlation of dyads within the same cluster (i.e. professional), assuming an average cluster size of four and an intracluster correlation coefficient of 0.05. Assuming a 25% dropout rate of patient-caregiver dyads, the study needed an final enrolment of 190 dyads in each trial arm. The economic evaluation is a cost-effectiveness analysis regarding a societal perspective. In the economic evaluation both costs and effects will be monetarized and consequently will result in a net benefit.