Background In idiopathic dilated cardiomyopathy, long-term outcome is poor and left ventricular ejection fraction is a major powerful predictor of survival. However, right ventricular function might also play an important role in the long-term prognosis of this disease. Aim The aim of this study was to determine the role of right ventricular parameters, mainly right ventricular ejection fraction, on survival in idiopathic cardiomyopathy. Methods We prospectively assessed long-term follow-up and predictors of survival in 62 consecutive patients referred from 1990 to 1992 for evaluation of idiopathic dilated cardiomyopathy, including haemodynamic evaluation, thermodilution right ventricular ejection fraction and volume measurements. Results At the time of catheterization, dyspnoea class III or IV was present in 60% of the patients, atrial fibrillation in 19% and complete left bundle branch block in 35%. Left ventricular ejection fraction was 30±10% and right ventricular ejection fraction was 30±l6%. During follow-up (2·2±1·3 years), 15 patients (24%) had heart transplantation and nine (14%) died before cardiac transplantation. Cumulative survival rate without heart transplantation was 74% and 56% at 1 and 4 years, respectively. In univariate analysis, survival was related to: dyspnoea class I or II (PPPPP0·002), high right ventricular ejection fraction (PPPPP<0·004). Conclusion In addition to left ventricular ejection fraction, right ventricular ejection fraction appears to be a complementary predictor of survival in idiopathic dilated cardiomyopathy, suggesting the importance of assessing right ventricular function in this disease.