Heart failure is a major health problem and is associated with a high mortality and morbidity. Recently, the role of the genetic background in the onset and development of the disease has been evidenced in both heart failure with and without systolic dysfunction, and in familial and non-familial forms of this condition. Familial forms of dilated cardiomyopathy are more frequent than previously thought. Various modes of inheritance and phenotypes have been reported and this condition appears genetically highly heterogenous. Five genes (dystrophin, cardiac actin, desmin, lamin A/C and delta-sarcoglycan), and additional loci, have been identified in families in which dilated cardiomyopathy is isolated or associated with other cardiac or non-cardiac symptoms. It has been postulated that the molecular defect involved could lead to abnormal interactions between cytoskeletal proteins, responsible either for defect in force transmission or for membrane disruption. More recently, the identification of mutations in genes encoding sarcomeric proteins has led to a second hypothesis in which the disease might also result from a force generation defect. In non-monogenic dilated cardiomyopathy, susceptibility genes (role in the development of the disease) and modifier genes (role in the evolution/prognosis of the disease) have so far been identified. Some data suggest that the efficacy of angiotensin converting enzyme inhibitors, and side-effects, might be related to some genetic polymorphisms, such as the I/D polymorphism of the angiotensin converting enzyme gene. Although preliminary, these data are promising and might be the first step towards application of phamacogenetics in heart failure. This is of paramount importance as the medical treatment of heart failure is characterized by the need for polypharmacy. One of the major challenges of the next millenium, therefore, will be to identify genetic factors which might help define responders to major treatment classes, including angiotensin converting enzyme inhibitors, beta-adrenoreceptor antagonists, angiotensin AT1 receptor antagonists, spironolactone, vasopeptidase inhibitors and endothelin receptor antagonists.