Hypertrophic cardiomyopathy (HCM) is a genetic cardiac disease characterized by left ventricular (LV) hypertrophy. There is often associated LV diastolic dysfunction and myocardial ischemia. The severity of the LV hypertrophy, diastolic dysfunction, and myocardial ischemia are important determinants of clinical outcomes. Angiotensin II modulates cell growth and cardiac function. There is also increasing evidence that the renin-angiotensin system (RAS) may be present in cardiac cells, and the hypertrophic action of angiotensin II could therefore be mediated by circulating or locally produced hormone. Animal and clinical studies have demonstrated that independent of their effects on systemic blood pressure, ACE inhibition and angiotensin II receptor (AT1) blockade can reduce cardiac hypertrophy, improve LV diastolic function and myocardial ischemia. AT1 blockade may be preferable to ACE inhibitors because by inhibiting angiotensin II from binding to its receptor, the system can be turned off irrespective of the source of angiotensin II. Also, there may be fewer side effects due to lack of bradykinin. This is a double-blind, placebo-controlled study that examines the abilities of enalapril (ACE inhibition) and losartan (AT1 blockade), separately or in combination, to cause regression of the cardiac hypertrophy, and to improve LV function and myocardial perfusion in non-obstructive HCM.