In this paper, a model for assessment and intervention is presented. This model explains how to perform theory- and evidence- based as well as practice-based assessment and intervention. The assessment model applies a holistic approach to treatment planning, which includes recognition of the influence of community, school, peers, family and the functional and structural domains of personality at the behavioural, phenomenological, intra-psychic and biophysical level in a dialectical developmental process. One important aspect of the theoretical basis for preparation of this model is that the child's personality must be understood in terms of the historical development. This assessment and intervention model focuses equally on strength and virtues as well as obstacles against development within the individual and its relations. Finally, guidelines for how to measure outcome are provided. (Contains 6 figures and 35 footnotes.)