We present a case of an 18-year-old boy with neurofibromatosis type 1 and hypertrophic cardiomyopathy with systolic anteward movement of the anterior leaflet of the mitral valve. Gradient in the left ventricular outflow was 85 mm Hg secondary to subvalvular aortic stenosis with left ventricular diastolic dysfunction. The possibility of a coincidence, or a causal relationship of these 2 conditions is mentioned.