Up to now only 30 to 40% of patients who die suddenly can be identified as likely candidates before the event. Risk factors in these asymptomatic subjects include a familial history of coronary artery disease, high blood cholesterol levels, hypertension, smoking and, more importantly, an abnormal ECG at rest or during exercise. The predictive value of these abnormalities is too low to justify more detailed clinical investigations in most of these asymptomatic subjects. Exceptions might be the group of patients with multiple risk factors and competitive sportsmen. Sudden cardiac death is a well known complication in patients with hypertrophic and dilated cardiomyopathy. Risk factors in hypertrophic cardiomyopathy include a familial history of this disease, syncope and increasing age. Furthermore, in the adult, the presence of nonsustained episodes of ventricular tachycardia during Holter monitoring seems to indicate an increased risk of sudden cardiac death. In idiopathic dilated cardiomyopathy, the presence of frequent episodes of ventricular pairs and/or episodes of ventricular tachycardia during Holter monitoring, together with a reduced left ventricular ejection fraction, characterises the patient at risk of sudden cardiac death. In patients with coronary artery disease, the patient at risk of sudden cardiac death can be identified by investigating the following: coronary anatomy; global and regional left ventricular function; the presence of ischaemia during rest and/or exercise; the presence of late potentials, by means of the signal-averaged ECG; the presence of spontaneous ventricular arrhythmias (especially sustained and nonsustained ventricular tachycardia); and the results of electrophysiological testing. On the basis of these investigations, 3 subgroups can be distinguished: patients at low risk, medium risk, and high risk of sudden cardiac death.