A number of remarkable similarities have been reported in certain spontaneously occurring myocardial disorders in domestic animals that closely resemble the clinical and phenotypic features of their corresponding diseases in humans. Chief among these conditions are hypertrophic cardiomyopathy (HCM) in the cat as well as arrhythmic right ventricular cardiomyopathy in cats and Boxer dogs, and non-hypertrophied restrictive cardiomyopathy in cats. Hypertrophic cardiomyopathy occurs commonly in the cat where it is a prominent cause of congestive heart failure and cardiovascular disability. Its prevalence in certain breeds suggests that it is a familial condition. Despite some inter-species differences in the expression of HCM in man and cats, their phenotypic expressions are very similar, supporting the belief that they are essentially the same disease in both species. These similarities include marked disease heterogeneity with unexplained asymmetric left ventricular hypertrophy, histopathology that includes disorganized myocyte arrangement, microvascular disease, and interstitial fibrosis, and end-stage cardiac remodeling. In cats two causal mutations have been identified in the myosin binding protein C (MYBPC3), though in man, mutations associated with 11 genes encoding for cardiac sarcomeric proteins are responsible for HCM.