In too many cases, the cause of dilated cardiomyopathy (DCM) remains undetermined. Coronary or valvular heart diseases, connective tissue disorders, toxic causes and signs of infection are systematically investigated. With the exceptions of coronary and sometimes valvular heart disease, the treatment of cardiac failure remains symptomatic treating the consequences but not the cause of DCM, which is therefore diagnosed as "idiopathic". This artericle reports the clinical history of 4 patients followed up for apparently "idiopathic" DCM in whom the presence of chronic Parvovirus B-19 infection was demonstrated. Based on these 4 cases, the hypothesis of an infectious cause of DCM and the role of myocardial biopsy, given the progress in molecular biology, are reconsidered. Parvovirus B-19 infection has recently been recognised not only as a cause of myocarditis but also of chronic viral cardiomyopathy, as in adeno and enteroviral infection. The authors conclude that the progress in molecular biology, the recognition of a viral aetiology and the efficacy of immuno-modulator therapy such as beta-interferon, may lead to a new management strategy of patients with DCM in cardiological referral centres.