OBJECTIVE: To analyze the construct validity, criterion validity, and the acceptance and understanding of the EQ-5D in patients with acute coronary syndromes (ACS). METHODS: All ACS-diagnosed patients discharged from a university-affiliated hospital during a 3-year period were mailed a questionnaire that included the EQ-5D and the SF-8. The EQ-5D includes a 100-point visual analogue scale (VAS) to measure self-reported current health-state and five items measuring mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Also included were disease severity measures [Duke Activity Status Index (DASI), cardiac symptom count (SC), patient-perceived cardiac disease severity], comorbidity measures (Charlson comorbidity index, total medication count), and other demographic and disease-related items. RESULTS: Of 1217 patients, 490 (40.3%) responded. Patients averaged 65.2 (± 11.3) years of age; 71.0% male; 91.9% Caucasian; 64.3% history of MI. Acceptance and understanding appeared high with only 0.2% - 0.4% of EQ-5D items and 8% of the VAS unanswered. Correlations between the VAS score and DASI/SC/perceived severity were rs = 0.741/rs = -0.615/rs = -0.455 (all p <0.0001). Levels of responses to EQ-5D items and the VAS score were significantly better for patients with very mild/mild perceived disease severity compared to severe/very severe, and for patients with a DASI = 18 compared to a DASI < 18. VAS score and SF-8 subscale score correlation coefficients ranged from 0.526-0.764 (all p <0.0001). Significant differences were observed between the response level of individual EQ-5D items and scores of comparable SF-8 subscales. The nine most common health states were identified based on the five EQ-5D item scores. As health status diminished there was a decline in the VAS, DASI and satisfaction with current health state, and an increase in the perceived severity, comorbidity score, SC, and medication count. CONCLUSIONS: The EQ-5D was easily understood and accepted by this cohort of patients with ACS and can serve as a valid measure of health-related quality of life in ACS population-based studies.