Cardiomyopathies are serious heart muscle disorders in children and adults, which result in morbidity and premature death. These disorders include hypertrophic cardiomyopathy, dilated cardiomyopathy and restrictive cardiomyopathy. Recently, mutations in seven genes, all encoding sarcomeric proteins, have been identified as causes of familial hypertrophic cardiomyopathy. The genes include those encoding the beta-myosin heavy chain, alpha-tropomyosin, cardiac troponin T, myosin binding protein-C, myosin essential light chain, myosin regulatory light chain, and troponin I. Advances in the understanding of dilated cardiomyopathy have been made recently as well and it appears as if cytoskeletal proteins play a central role. Dystrophin has been identified as the gene responsible for X-linked dilated cardiomyopathy and this protein, which is also responsible for Duchenne and Becker muscular dystrophy, plays an important role in myocyte and cardiomyocyte function. Mutations in other cytoskeletal proteins such as metavinculin, alpha-dystroglycan, alpha- and gamma-sarcoglycan, and muscle LIM protein have also been found to result in dilated cardiomyopathy, suggesting that cytoskeletal proteins play a central role in cardiac function.