Hypertrophic cardiomyopathy has been shown to be a genetically heterogeneous disorder, linked to at least four different loci on chromosomes 14, 1, 15, and 11. Thus far, three genes have been identified that harbor mutations leading to hypertrophic cardiomyopathy. These genes--cardiac beta myosin heavy chain, alpha tropomyosin, and troponin T--code for proteins that are integral components of the sarcomere. Other loci and genes remain to be identified. Certain genotype-phenotype correlations appear to exist.