Objective: Few data exist regarding the prognostic value of QT dispersion in hypertrophic cardiomyopathy (HCM). In this study, we prospectively investigated the association between baseline QT dispersion and clinical course of HCM. Methods: Overall, 101 patients with asymmetric septal hypertrophy (59 men, mean age 45±16 years, range 13-74 years) were included in the study and were followed up for 595±367 days for clinical endpoints defined as cardiac death and hospitalization due to worsening in heart failure symptoms. QRS duration, QT interval, and JT interval were manually measured on 12-lead electrocardiogram (ECG). QT dispersion and corrected QT dispersion were calculated accordingly. The ECG findings of the patients with and without clinical endpoints were compared. Results: Twenty-nine patients experienced clinical endpoints (3 sudden deaths, 26 hospitalizations due to worsening heart failure). The measurements of QT, JT and QRS intervals were all comparable between the two groups (p>0.05 for all). QT dispersion and corrected QT dispersion were significantly different between patients with and without clinical endpoints (64±30 ms vs. 83±18 ms and 71±33 ms vs. 90±18 ms, respectively, p=0.001 for both). Corrected QT dispersion >80 ms detected patients with clinical endpoints with sensitivity and specificity of 79% and 75%, respectively. Patients with corrected QT dispersion <80 ms were significantly free of clinical endpoints. Conclusion: In conclusion, for patients with hypertrophic cardiomyopathy, measurement of baseline corrected QT dispersion from surface ECG may be used to identify those at risk for clinical deterioration at long-term follow-up.