The Doppler echocardiographic pattern of restrictive left ventricular (LV) filling has proved to be an important predictor of clinical course and prognosis in dilated cardiomyopathy. However, the relation between restrictive filling pattern and clinical course has not been systematically investigated in hypertrophic cardiomyopathy (HC). We assessed the prognostic implications of the Doppler restrictive filling pattern in 239 consecutive patients with HC in whom Doppler measurements of LV filling had been systematically recorded at initial evaluation and during follow-up. Restrictive LV filling was identified in 14 patients (5.9%) at initial evaluation and developed in 22 (9.2%) during follow-up. A close relation was identified between restrictive filling pattern and end-stage HC, with patients with restrictive filling showing a sixfold increase in risk of developing end-stage HC (hazard ratio 6.25, 95% confidence interval 1.90 to 20.57, p = 0.003). Over a median follow-up of 9.7 years, 22 patients (9.2%) died suddenly or received appropriate cardioverter-defibrillator interventions, and 54 (22.6%) had HC-related death or underwent heart transplantation. In a set of univariate and multivariate analyses including each of the generally accepted risk factors for cardiac death in HC, the restrictive filling pattern was a strong and independent marker of increased risk (hazard ratio for sudden cardiac events 3.51, 95% confidence interval 1.37 to 8.95, p = 0.009; hazard ratio for HC-related death or heart transplantation 3.54, 95% confidence interval 1.91 to 6.57, p <0.001) compared to patients without restrictive filling. In conclusion, in our study cohort, the Doppler pattern of restrictive LV filling proved to be a strong predictor of sudden death and HC-related death, independently of other markers for unfavorable prognosis in this disease.