The last 20 years have seen impressive progress in the study of cardiomyopathies. The improved understanding of these diseases has made clear that cardiomyopathies are extremely complex entities that defy current classification standards. The 1980 and 1995 WHO/ISFC Task Forces, and very recently an American Heart Association (AHA) Scientific Statement expert panel, have systematically approached new advances as well as emerging problems. In spite of this effort and an increasingly growing understanding of myocardial disorders, several issues remain unresolved. Without a doubt, the identification of genetic defects responsible for many forms of cardiomyopathies has changed our perspective of myocardial diseases. In fact, in the last few years, we have seen that (1) clinically defined cardiomyopathies, previously considered single entities, are actually the result of mutations in different genes, (2) different mutations in the same gene may be the cause of different clinical entities and (3) in the group of cardiomyopathies, a large phenotypic and genetic heterogeneity exists that is expected to increase in the future. Genotype knowledge is a fundamental advance in medicine and in particular in the field of cardiomyopathies and is becoming increasingly more important in clinical practice for disease diagnosis and prevention, prognostic stratification and possible future therapies. Knowledge of the phenotype, including clinical, morphological and physiological features, however, continues to provide the clinical basis for diagnosis and classification of cardiomyopathies, prognostic evaluation and symptomatic treatment, and should not be abandoned.