DRG use has spread through most European countries thus offering an opportunity for improving hospital data bases at the European level. An EEC Concerted Action 'Use of DRGs to support Hospital Sector Management in the European Community' was approved by the Committee of Health Services Research of the EEC. A general overview of the project is presented as well as a detailed description of the results of the work on aspects related to DRG data production. These aspects (MBDS implementation and variables definition; coding systems and updating; mapping systems; data auditing; trimming methods; and DRG grouper versions) have been analyzed with the objective of increasing opportunities for valid international comparisons of DRG statistics between European countries.