Hypertrophic cardiomyopathy (HCM) was first described more than a century ago; the characteristic finding is an inappropriate myocardial hypertrophy, occurring in the absence of an obvious cause. Determination of the exact site of the hypertrophy and of the obstruction of the left ventricular outflow tract, in asymmetric septal hypertrophy, establishes which is the best treatment strategy. Forty-one-year-old man with a history of recurrent palpitations without any other symptomatology. The initial electrocardiogram (EKG) showed sinus rhythm with evidence of ventricular left hypertrophy and unspecific changes in ventricular repolarization. The transthoracic echocardiogram showed HCM and mitral regurgitation. The electrophysiological study, under treatment with amiodarone, did not induce ventricular arrhythmias. The 10-years evolution of the EKG showed changes of variable degrees associated with the hypertrophy and systolic overload of the left ventricle. The echocardiographic three-dimensional reconstruction in the long axis revealed the dynamic obstruction of the left ventricular outflow tract. In the hemodynamic study, the existence of a subaortic gradient confirmed the diagnosis and showed an increase of the gradient at the post-extrasystolic beat (Brockenbrough-Braunwald phenomenon). The echocardiographic three-dimensional reconstruction defines more accurately the exact site of the septal hypertrophy and its hemodynamic consequences.