Abstract Background We evaluated the accuracy of physician recognition of functional status impairment in older emergency departments (ED) patients. In particular, we evaluated the accuracy of medical records (a comparison of the information in the medical record with the functional status based on proxy interviews), and the accuracy of physician knowledge (a comparison of the information obtained from the responsible physician with the functional status based on proxy interviews). Methods Cross-sectional study on 101 frail older patients selected at random from among those attending ED, their ED physicians, and respondents. The study was conducted at ED in four general university teaching hospitals in a city, from July through November 2003. Functional data shown on patients' medical records were compared against functional data obtained from respondents (family members), using Kendall's Tau-b statistic. In addition patients' Katz Indices (which assesses six basic activities of daily living – basic ADL) based on interviews with ED physicians were compared against those obtained from respondents, using the coefficient of concordance weighted kappa (κ). Each patient and his respondent were paired with a single physician. Results The correlation between information on dependence for basic ADL obtained from medical records and that furnished by respondents, was 0.41 (95% CI 0.27–0.55). Concordance between the respective Katz Indices obtained from physicians and respondents was 0.47 (95% CI 0.38–0.57). Conclusion Older subjects' functional status is not properly assessed by emergency department physicians.