Apical segmental dysfunction is an unusual finding in hypertrophic cardiomyopathy (HCM). It is characterized by a poor clinical course and a high incidence of malignant ventricular tachyarrhythmias. Long-term prognosis of patients with HCM and apical segmental dysfunction is still unclear. We report 2 cases of apical segmental dysfunction in HCM in whom progressive apical dilatation and congestive heart failure developed. Both patients died suddenly, and intractable ventricular tachyarrhythmias were documented in 1 case during resuscitation. This report provides further evidence that apical segmental dysfunction might predict a subgroup of patients with HCM who are likely to develop end-stage heart failure and are at high risk of sudden cardiac death.