In the WHO/ISFC classification of 1996, cardiomyopathies were defined as primary myocardial disorders of unknown cause. Heart muscle disorders of known etiology or associated with systemic disorders were classified as secondary or specific heart muscle diseases. An expert panel of the American Heart Association has recently suggested a new scheme that combines genetic and clinical criteria. In this system, the term primary is used to describe cardiac diseases in which the heart is the sole or predominantly involved organ and secondary to describe diseases in which myocardial dysfunction is part of a systemic disorder. In a radical departure from convention, they also suggested that ion channelopathies and disorders of conduction should be considered cardiomyopathies as well. The ESC Working Group on Myocardial and Pericardial Diseases has taken a different approach based on the belief that a clinically oriented classification system in which heart muscle disorders are grouped according to ventricular morphology and function remains the clinically most useful method for diagnosing and managing patients and families with heart muscle disease. In the ESC position statement, cardiomyopathies are defined as myocardial disorders in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. In this article, this is illustrated by examples of dilated cardiomyopathy as familial/genetic forms and nonfamilial/nongenetic forms.