Pathologists are faced with an increasing complexity in the cardiac diseases that cause sudden natural death in the absence of coronary artery disease. A significant proportion of such natural sudden deaths are due to familial heart muscle disease (cardiomyopathy). The phenotypic characteristics of both hypertrophic cardiomyopathy and arrythmogenic right ventricular dysplasia are wider than previously thought and the hearts may be very close to normal on naked eye examination. Detailed histology of the myocardium is needed to identify such cases. Up to 200 sudden deaths a year in England occur in young, apparently fit individuals in whom toxicology and detailed examination of the heart for structural abnormalities is negative. Genetic defects in ion channels (long QT interval) are now known to be one cause of this phenomenon. In investigating a case of sudden death without cause, a study of the family -- if they wish it -- may be helpful in arriving at a cause.