A method for initiating quality assurance in cardiac surgery was developed multicentrically by a commission of the German Society for Thoracic and Cardiovascular Surgery (QUADRA Study). To appraise the quality of cardiosurgical action, variables were compiled from the preoperative, intraoperative, and postoperative treatment course. The data collection was carried out at the same time as treatment. On the basis of unicentric data profiles, multicentric hospital profiles, and problem profiles, a quality comparison could be carried out and the variability of cardiosurgical action which may occasion interventions could be identified. A reduction of perioperative blood consumption during the study period could be observed in four out of five hospitals as the first result. The data collection also revealed epidemiological features. On average, women were older than men at the time of the heart-valve and coronary operations. To ensure data validity and the organization of quality assurance, a documentation assistant and a specially trained physician are necessary at every cardiovascular surgery center. The multicentric external comparison is indispensable and must be carried out by means of a central data collection, for which intrumental and staff capacities are also to be provided. With modern methods of data processing, an additional and new approach to the improvement of quality in cardiac surgery can thus be made.