OBJECTIVE - To provide an overview of databases that are maintained by the Department of Veterans Affairs (VA) and are of relevance to investigators involved in epidemiologic, clinical, and health services research. RESEARCH DESIGN AND METHODS - We reviewed both national and local VA databases and identified their strengths and limitations. We also referenced specific studies that have assessed the validity and reliability of VA databases. RESULTS - There are numerous national databases housed at the Austin Automation Center in Austin, Texas. These include the Patient Treatment File (hospital abstracts), the Outpatient Care File, the Beneficiary Identification Record Locator System death file for assessing vital status, and the Decision Support System, which provides integrated clinical and financial information for managerial decision making. The major limitation of these databases is that clinical detail below the level of ICD-9-CM diagnosis and procedure codes is not uniformly available nationally. These databases offer an excellent opportunity to monitor the health of veterans over time because they track all inpatient and outpatient utilization in the VA. However, at the local or medical center level, the Veterans Health information and Systems and Technology Architecture contains extensive clinical information, but has fewer patients, varies in format across medical centers, and poses difficulties with data extraction for statistical analysis. CONCLUSIONS - Both local and national VA databases are valuable resources for investigators who have interests in a wide array of research topics, including diabetes. The potential for investigating important scientific questions with VA databases becomes greater as communications and database management technologies improve.