The usual diagnostic systems of the ICD and the DSM offer no adequate solution to the problem of classification and assessment of social dysfunction. Social dysfunction as a consequence of disease or disorder has been conceptualised in terms of (social) disabilities, and (role) handicaps (according to the ICIDH 1980) and as activities limitations and participation restrictions (according to the ICF 2001). Conceptual models of disability or social dysfunction reflect various ways of a normative perspective on a person's integration in the community and determine to a large extent its measurement, which has been criticised because of this perspective but also with respect to the independence of psychopathology, actual behaviour, opportunities, criteria of assessment, source of information, etc.. These crucial issues in the assessment of disability will be addressed from a methodological point of view.