Health services research investigates the supply of individuals and the population with health-relevant products and services under routine daily conditions. It must be understood as a cyclic process whereby an image of the current situation should always be the starting point but which can, for example generate hypotheses for new approaches in clinical research. Health services research cannot be reduced to a specific method but is primarily defined by the question to be answered. The use of health insurance data in particular play a major role in health services research.