Researchers have frequently relied on case identification using clinician-based screening as the standard. This study evaluates a self-administered screening questionnaire developed for use in the Veterans Health Study. We compared concordance between elderly patients' reports of selected chronic illnesses and the medical record. The purpose of this study was to determine the feasibility of using a self-report screening questionnaire for case identification in an outcomes study of elderly respondents. Reports of the presence of selected chronic illnesses were compared in a sample of patients (N=402) receiving outpatient care between 2 data sources, patient self-report and medical record, to determine overall concordance in 5 common chronic conditions (hypertension, adult-onset diabetes mellitus, chronic low-back pain, osteoarthritis of the knee, and chronic lung disease). Discordance between the 2 data sources varied by condition. Differences in reporting were small for diabetes and hypertension, intermediate for chronic lung disease, and larger for osteoarthritis of the knee and chronic low-back pain, where the chart did not identify substantial proportions of cases reported in the questionnaire. Use of patient-reported screening questionnaires, which are self-administered, is a valid, cost-efficient method to identify some chronic illnesses. Using medical records alone may result in underestimation of some symptom-based conditions.