The authors report two cases of hypertrophic obstructive cardiomyopathy in young girls, age 3 months and 8 years old. The disease manifested itself as a cardiac heart failure in the infant's case and a syncop in the other case. Cardiac echocardiography showed in he first case asymetric hypertrophic cardiomyopathy with ventricular outflow tract obstruction gradient of 100 mmhg, and concentric hypertrophic with 120 mmhg in the second case. Its evolution was fatal in both cases and led to sudden death at home. This disease is severe as no therapeutic treatment can modify its course.