With a population of 82.5m, Germany represents the largest health care market in Europe. Yet, research into epidemiology, resource utilization, and actual cost associated with specific disorders has been hampered by the fragmentation of the national health care system. OBJECTIVES: 1) To establish an integrated claims database in the German region of Nordbaden, allowing retrospective patient-based analyses; 2) to evaluate how representative the selected sample may be considered for Germany as a whole; and 3) to assess its potential by determining administrative prevalence rates of ADHD. METHODS: The complete claims database of the official physicians' organization of Nordbaden (KVNB) in South-Western Germany for the 4 quarters of 2003 was first coded to protect the privacy of patients and physicians, and subsequently integrated and restructured according to patient pseudonyms, as to allow patient and disease specific cross-sectional analyses. Sociodemographic and health care related characteristics of the sample population were compared with data for West Germany, East Germany, and Germany as a whole. One-year prevalence rates were determined for attention-deficit/hyperactivity disorder (ADHD). RESULTS: Claims data for 2.238m persons insured by the SHI (82.2% of the regional population; cf. Germany: 70.4m or 85.3% SHI insured) were available, representing – as judged by key sociodemographic and medical indicators (which will be presented) – the German SHI insured population. ADHD (hyperkinetic disorder: ICD-10, F90.0, F90.1) prevalence rates were: age 0-6: 1.26% (boys: 1.72%, girls: 0.77%), age 7-12: 4.97% (boys: 7.15%, girls: 2.66%), age 13-19: 1.31% (males: 1.91%, females: 0.60%), and adults: 0.04% (males: 0.04%, females: 0.03%). CONCLUSIONS: Especially when combined with data from regional hospitals and sick funds, databases like the “Nordbaden Project” will provide a valuable tool for studies of real-world health care utilization and direct medical costs associated with defined medical conditions. Specific findings on ADHD will be discussed in light of international epidemiological data.