The criteria by which healthcare is judged or measured are quality, accessibility, and cost effectiveness. To evaluate these criteria it is important to have a database. There are many strengths and weakness to large databases. They can be used as an indicator of the level of performance or quality, for clinical decision making, and as a measurement of cost effectiveness. They can also be useful in the evaluation and development of treatment algorithms and critical pathways for patients with entry level disease. In addition, they can measure patient access to healthcare and the appropriateness of care. It is important for these databases to appropriately adjust for preoperative risk factors that may influence outcome. Outcome in most of the databases is measured by mortality, but morbidity, functional status, quality of life, cost of care, length of stay, return to work, and patient satisfaction are also important outcomes. Factors that can influence the quality of the outcome data are the methods by which the data are collected, standardization of definitions, the currentness of the database, adequate numbers of patients and outcomes, and appropriate analytic techniques. It is important to feed back the data to the healthcare providers in a timely enough fashion so that processes and structures of care can be modified to improve treatment and results. The reliability of the databases and the validity must be substantiated for the healthcare provider to have confidence in the database.(ABSTRACT TRUNCATED AT 250 WORDS)