DILATED CARDIOMYOPATHY - Conduction and rhythm disturbances are frequent findings in dilated cardiomyopathy. 65 patients with dilated cardiomyopathy underwent 24-hour electrocardiographic monitoring: 95.4% showed ventricular arrhythmias, 80% complex ventricular arrhythmias and 44% runs of non-sustained ventricular tachycardia. Over 1000 ventricular extrasystoles in 24 hours were present in 44% of cases. Ventricular tachycardia and multiform and paired ventricular extrasystoles correlated significantly with the severity of cardiac dysfunction and with a worse prognosis. Patients undergoing antiarrhythmic therapy (amiodarone) showed a significant reduction in the number of ventricular extrasystoles and in the incidence of complex ventricular arrhythmias. HYPERTROPHIC CARDIOMYOPATHY - The high incidence of arrhythmias, particularly ventricular arrhythmias (approx. 70% of cases) in hypertrophic cardiomyopathy is well recognized: episodes of ventricular tachycardia are present in 20% of cases and are related to an elevated risk of sudden death. Antiarrhythmic treatment with amiodarone significantly reduces the number of ventricular extrasystoles and the episodes of ventricular tachycardia, may prevent sudden death and improve survival. RESTRICTIVE CARDIOMYOPATHY - Very little information is present in literature concerning this extremely rare form, in which every type of rhythm and conduction disturbance has been observed. CONCLUSIONS - Electrocardiographic monitoring is nowadays a very important tool in the management of cardiomyopathy patients, to identify possible patients at risk and to monitor the antiarrhythmic treatment.