BACKGROUND: Stroke registries contribute to the conduct of clinical research and to the assessment of health care quality control. Efforts to compare clinical outcomes and quality indicators between centers are dependent on standardized data elements, but it is unknown how stroke physicians define common data elements, such as hypertension or diabetes, when collecting data for registries at their centers. METHODS: We conducted an internet-based survey of 91 centers affiliated with a university to assess their definitions of common data elements (CDEs) and compared their responses with standardized definitions, including those from the American College of Cardiology (ACC). RESULTS: More than half (52%) of centers completed the survey. There was only modest agreement among respondents regarding definitions of CDEs in the survey and even less agreement on how the respondents' definitions compared to ACC standards. CONCLUSIONS: Surveyed respondents do not agree on the definitions of CDEs, making comparisons between centers problematic. Standardized definitions of CDEs are needed to improve data collection for patient care and clinical research.