Fifty percent of patients with dilated cardiomyopathy die within 5 years of diagnosis. Syncope is known to be a predictor of poor outcome in patients with advanced heart failure. To assess the risk of patients with dilated cardiomyopathy with a history of syncope during standard medical treatment we compared this group to similar patients without syncope. Twenty-three patients with angiographically proven dilated cardiomyopathy and syncope were followed prospectively and compared to 201 patients without history of syncope. All patients showed a left-ventricular ejection fraction of less than 45%. Both groups did not differ in left-ventricular ejection fraction at baseline (30 +/- 7% in the syncope group, 30 +/- 8% in the no syncope group). Mean follow-up was 2.6 years in the syncope group and 2.4 years in the no syncope group. At baseline, syncope patients used more often amiodarone (p < 0.04), while there was no statistically significant difference between the two groups regarding the intake of digitalis, diuretics and angiotensin-converting enzyme inhibitors. Twenty-six percent of patients in the syncope group and 20% in the no syncope group died during follow-up (non significant). The striking difference, however, was the type of death: 5 out of 6 patients in the syncope group died suddenly compared to 13 of 41 patients in the no syncope group (p < 0.025). Patients with dilated cardiomyopathy and a history of syncope are at high risk of sudden death.