PURPOSE: Development of an algorithm for computer-assisted dose reconstruction using exposure data from a very large electronic database of a university children's hospital. Radiation dose values and new conversion factors for pediatric radiology were calculated and selected results for skull X-rays of 5-year-old patients will be presented. MATERIALS AND METHODS: Since 1976 all relevant data from daily routine X-ray examinations performed in Dr. von Hauner's Kinderspital (children's hospital of the university of Munich, DvHK) have been stored electronically in a database. This database now encompasses basic personal patient data, type of radiological procedure, individual radiographic/fluoroscopic settings, dose measurements (dose area product), individual referral criteria and radiological diagnosis. After 30 years of data gathering, the database now includes 305 434 radiological examinations (radiographs and fluoroscopies) of all age groups, from newborns to adolescents. With a computer program, called PADOS, a specific algorithm was created to calculate radiation doses using the individual dose area product values and other known exposure parameters extracted from the databases. The dose reconstruction procedure is based on the conversion factor concept. By means of the PCXMC program developed by the Finnish Center for Radiation and Nuclear Safety (STUK, Helsinki), Monte Carlo simulations were performed to calculate new conversion factors for pediatric radiology based on the radiographic technique used in the DvHK. RESULTS: The entrance dose values of skull X-rays showed a very good correlation with the changes of examination technique in the last 30 years. In our sample, the measured dose values for skull X-rays were far below the reference dose levels set by the Bundesamt für Strahlenschutz (BfS) in 2003. Conversion factors for 28 different radiographic procedures, 6 age groups, 40 reference organs, 3 beam projections, 12 voltage settings and 3 total filtration levels were calculated. The influence of collimation on the organ doses of radiosensitive organs, e. g. thyroid, bone marrow, in all age groups, especially in the very young, was able to be demonstrated. CONCLUSION: The PADOS algorithm seems to be suitable for the handling of very large and heterogeneous radiological databases and allows the reconstruction of various dose entities.