Many studies on the natural history of dilated cardiomyopathy show high probability of death or of cardiac transplantation in a large percentage of patients. These studies have several methodological limitations. Our prospective study, carried out from 1971, and which evaluated 120 patients, showed improved survival in more recent years. Survival 3 years after diagnosis changed from 30% (1971-6/1981) to 88.4% (7/1986-1/1989). Thirty patients were investigated by haemodynamic exercise test to assess their haemodynamic behaviour during exercise, to evaluate the effects of pharmacological treatment and to define parameters of prognostic value. Different haemodynamic behaviours were observed. Haemodynamic investigation during exercise is useful to assess the effect of treatment and may have prognostic value. Myocarditis presents a spectrum of clinical symptoms and echocardiographic abnormalities. In patients with congestive heart failure left ventricular dysfunction is common. Patients with atrioventricular block or chest pain usually have good left ventricular function. During follow-up, improvement is possible but persistent left ventricular dysfunction is associated with a high mortality rate. When left ventricular function is good at presentation and does not deteriorate during follow-up the prognosis is good.