ATC-ICD is a two step statistical technique. In step 1, based on hospital and sick leave diagnoses and medication received by the insured and co-insured persons over a defined period of time) assignment probabilities to diagnoses were calculated. In step 2, these assignment probabilities are applied to the prescription data of all persons who have used social insurance services, which anables an estimate of diseases probabilities to be made. The calculations are based on the GAP-DRG 2006/2007: The GAP-DRG (Grundlagenforschung für ambulante, personenbezogene „Diagnoses related Groups“) is a research database of the Association of Austrian Social Security Institutions that is used for the development of methods (method: ATC-ICD). It contains reimbursement data of all social health insurance funds as well as the diagnostic data of hospital admissions and sick leaves for the years 2006 and 2007.