One hundred and sixteen patients (mean age 46 years) with dilated cardiomyopathy documented by haemodynamic investigations and angiography with normal coronary arteriography were followed up for a mean period of 29 +/- 19 months. During that period, 36% of the patients died after a follow-up of 30 +/- 20 months. The actuarial death rates were 15% at 2 years, 45% at 6 years and 60% at 10 years. The main factors predictive of survival at 10 years were the clinical and haemodynamic markers of left heart failure. The death rate was multiplied by 1.6 in patients in stages III or IV of the NYHA classification (83% vs 51%, p less than 0.01), by 2.6 in patients with left ventricular end-diastolic pressure above 15 mmHg (73% vs 29%, p less than 0.01), by 2.2 when the indexed end-diastolic volume rose above 200 ml/m2 (75% vs 35%, p less than 0.01), by 2.2 when the left ventricular ejection fraction was below 40% (75% vs 35%, p less than 0.05) and by 2.6 when angiographic mitral valve regurgitation was present (75% vs 34%, p less than 0.01). The death rate at 9 years was 2.3 times higher in patients with left bundle branch block (72% vs 36%, p less than 0.05). A cardiothoracic index over 0.60 proved to be of poor prognosis at one year (death rate: 19%). While alcoholism played no part in the prognosis, the death rate in smokers was consistently higher than in non smokers (56% vs 32% at 6 years, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)