Reliable data on the prevalence and incidence of the spectrum of mental disorders in older people are currently lacking for the EU. Despite the availability of some national and a few cross-national cross-sectional studies with quite variable results, the size and burden of mental disorders in the elderly remains unclear. This has been attributed to a number of methodological factors (e.g. lack of appropriate diagnostic instruments). In addition patterns of incidence and of the natural course and prognosis of mental and physical disorders in people above 65 years are lacking nationally and cross-nationally in the EU, with only a few notable exceptions. Furthermore, there are no cross-national studies investigating the interaction of mental disorders and the utilisation of treatment under specific consideration of the severity and the impairment of activities and participation, in terms of ICF-categories, of older people in different European countries. Therefore, the objective of the proposed study is to (1) develop, respectively to adapt existing instruments and (2) to collect data on the prevalence, the incidence and on the natural course and prognosis of mental disorders, and to do this in sufficiently powered representative samples of older people living in the community across different European countries. This includes assessing health service needs, investigating to what extent existing services are used by older people and which specific barriers to utilisation may exist. Thereby, the implementation of the study will enable the further development and improvement of harmonised instruments for the assessment of impairments of activities and participation in older adults, to adapt already existing instruments, and to facilitate results that are comparable across cultures. Results will help to change health care in direct contact with people, and beyond this, they offer starting points for structural changes initiated on the level of health politics.