Background: Information on the developing process and on data validity is crucial when using health insurance claims data (on medications) for research purposes. In Germany, different prescription forms are available for narcotics (so-called 'Betäubungsmittelrezepte') and other medications (so-called 'Muster 16'). The aim of this study was to compare the correctness of the recorded research relevant information between them. Methods: We used data of the Gmünder ErsatzKasse (GEK) for the year 2006. Out of 7.2 million prescriptions we drew a simple random sample of 600 prescriptions for narcotics and 600 for other medications. Data on the scanned original prescription, which was used as a gold standard, were validated against that information in claims data. Results: Compared to prescriptions for other medications, dates of prescription (92.5% vs. 68.1%; p