Cardiomyopathies comprise a heterogeneous group of primary heart muscle disorders with a strong genetic component. Nearly all cases of hypertrophic cardiomyopathy and at least 20-30% of cases with dilated cardiomyopathy are due to autosomal dominant mutations. The extent of genetic factors for arrhythmogenic right ventricular and restrictive cardiomyopathy is less clear. Recent studies have demonstrated that genetic causes of all cardiomyopathies are highly heterogeneous with more than 25 disease gene loci. Although the ability to diagnose cardiomyopathies at the molecular level has advanced, our understanding of disease pathways and the knowledge of individual diseases causing mutations has had little impact on the clinical management of patients. Once current technical limitations for large-scale mutation analysis are overcome, broad genotype/phenotype correlation studies may answer important clinical issues such as the precise relation between distinct mutations and the risk of sudden death, course of the disease and treatment of patients.