Two patients with hypertrophic cardiomyopathy are reported from the recent experience of the Hypertrophic Cardiomyopathy Center of the Minneapolis Heart Institute Foundation, demonstrating limitations in the risk stratification algorithm currently used for this disease. One patient, an asymptomatic 21-year-old male college student, was prophylactically implanted with a cardioverter-defibrillator. This decision was based largely on the presence of apparent extensive myocardial fibrosis identified by contrast-enhanced cardiovascular magnetic resonance imaging, currently not considered a risk factor in this disease. Fifteen months later, ventricular fibrillation was interrupted by an appropriate defibrillator shock. The other patient, an asymptomatic 15-year-old male subject without any apparent high-risk markers, died suddenly at home. Necropsy examination of the heart identified scarring confined to portions of both left ventricular papillary muscles, possibly representing a substrate for ventricular tachyarrhythmias. In conclusion, these 2 cases demonstrate that present strategies for assessing high-risk status in hypertrophic cardiomyopathy are inadequate to identify all such patients. However, while the anecdotal nature of these observations cannot yet justify altering the general guidelines for implantation of defibrillators for the primary prevention of sudden death related to hypertrophic cardiomyopathy, 1 of our 2 cases suggests a future role for contrast-enhanced cardiovascular magnetic resonance in the risk stratification of this complex disease.