Hypertrophic cardiomyopathy (HCM) is a common genetic cardiovascular disorder (autosomal dominant transmission), with primary involvement of the myocardium and a prevalence range of 1:200 to 1:500 based on diverse phenotypic expression. If associated with resting or provoked left ventricular outflow tract (LVOT) obstruction ≥30 mm Hg, it is called hypertrophic obstructive cardiomyopathy (HOCM). HCM is characterized by localized or generalized unexplained left ventricular hypertrophy (maximum LV diastolic wall thickness ≥15 mm or 13–14 mmm in the presence of family history) in the non-dilated ventricle in the absence of any cardiac or systemic disease that can result in this magnitude of hypertrophy. Asymmetric septal hypertrophy (ASH) is a common finding (the ratio of IVS thickness to posterior wall thickness is ≥1.3/1) but is not characteristic of HCM. LVOT obstruction happens due to significant septal thickening and concomitant mitral leaflet systolic anterior motion (SAM), which is the abnormal movement (sharp bending) of the anterior mitral valve (MV) leaflet toward the interventricular septum during systole. The continuous-wave Doppler flow of the LVOT is characteristically dagger-shaped and late-peaking. MR due to SAM is a mid-to-late systolic, eccentric, and posteriorly directed jet. Several studies in patients with HCM have demonstrated a significant reduction in longitudinal strain (particularly in the mid-septal segment) with normal systolic twist or torsion. In this chapter, we review the role of echocardiography in diagnosis, risk stratification, and septal reduction myectomy.