Hypertrophic cardiomyopathy (HCM) is a rare cause of death among athletes, with deaths occurring in young, apparently healthy people. Differentiating HCM from conditioning hypertrophy is challenging. Routine detection involves family history, physical examination, electrocardiography, and echocardiography. Keys to differential diagnosis include evidence of heterogenous left ventricle hypertrophy, left atrial enlargement, unusual electrocardiograph patterns, and family history or gene mutations. (SM)