To create a valid, sensitive, disease-specific health status measure for patients with congestive heart failure (CHF). Quantifying health status is becoming increasingly important for CHF. The Kansas City Cardiomyopathy Questionnaire (KCCQ) is a new, self-administered, 23-item questionnaire that quantifies physical limitations, symptoms, self-efficacy, social interference and quality of life. To establish the performance characteristics of the KCCQ, two distinct patient cohorts were recruited: 70 stable and 59 decompensated CHF patients with ejection fractions of <40. Upon entry into the study, patients were administered the KCCQ, the Minnesota Living with Heart Failure Questionnaire and the Short Form-36 (SF-36). Questionnaires were repeated three months later. Convergent validity of each KCCQ domain was documented by comparison with available criterion standards (r = 0.46 to 0.74; p < 0.001 for all). Among those with stable CHF who remained stable by predefined criteria (n = 39), minimal changes in KCCQ domains were detected over three months of observation (mean change = 0.8 to 4.0 points, p = NS for all). In contrast, large changes in score were observed among patients whose decompensated CHF improved three months later (n = 39; mean change = 15.4 to 40.4 points, p < 0.01 for all). The sensitivity of the KCCQwas substantially greater than that of the Minnesota Living with Heart Failure and the SF-36 questionnaires. The KCCQis a valid, reliable and responsive health status measure for patients with CHF and may serve as a clinically meaningful outcome in cardiovascular research, patient management and quality assessment.