On July 1, 2009, the German Network for Health Services Research [Deutsches Netzwerk Versorgungsforschung e. V. (DNVF e. V.)] approved the Memorandum III "Methods for Health Services Research", supported by the member societies mentioned as authors and published in this Journal (Gesundheitswesen 2009; 71: 505-510). This is an in-depth publication on the "epidemiological methods for health services research". Legal, political and economic steps of intervention in the medical care system modify the health services structures and processes but the impact of such interventions on the medical care users has, so far and in general, not been examined scientifically. Due to this lack of evaluation, there is, also with regard to the economic situation within the health system, no transparency of potentially severe effects on healthy and, particularly, on ill people. For this very reason, the main questions and focuses of medical care research deal with prevalence, causes and effects of over, under and inappropriate supply of health services, the interaction between diagnostics and therapy, the processes across different sectors and the complex interdependences of health services. This part of the Memorandum of Deutsches Netzwerk für Versorgungsforschung e. V. (DNVF e. V., German Network for Health Services Research) will enumerate the methods and instruments that will be used for planned studies and that have been applied for finished studies of health services research and for the evaluation of its quality and value. Health services research takes advantage of the theories and the methods of the disciplines that are involved in its studies. It does not need a specific research methodology; its methods are adapted to the specific research question. It is rather to be expected that certain issues of this research branch and its access to data will lead to the development of new methods.
