Background. - To our knowledge, no histopathologic study of the differences between hypertrophic cardiomyopathy in different age groups or that contrasts the pathologic findings in the asymmetric septal hypertrophy and concentric hypertrophy forms of hypertrophic cardiomyopathy has been published. Method. - The clinicopathologic findings of younger (≤60 years) (n = 35) and older (>60 years) (n = 20) patients with hypertrophic cardiomyopathy were assessed. Each group was subdivided into groups of patients with asymmetric septal hypertrophy or concentric hypertrophy. Results. - Among the young patients, asymmetric septal hypertrophy was more prevalent than concentric hypertrophy, whereas among the elderly patients, concentric hypertrophy was more common. Sudden death was prevalent only among the young. Most young patients had a mirror image endocardial fibrous septal plaque, whereas most elderly patients with concentric hypertrophy did not. Ventricular septal myocyte disarray and intramural coronary artery thickening were far more marked among the young with asymmetric septal hypertrophy than the young with concentric hyperthrophy and the elderly. Conclusions. - Key differences exist between younger and older patients with hypertrophic cardiomyopathy. Much higher degrees of ventricular disarray and intramural coronary artery disease were noted in younger patients with asymmetric septal hypertrophy compared to the elderly patients and the younger patients with concentric hypertrophy.