To assess the prognostic significance of right ventricular function in dilated cardiomyopathy (DCM), we studied consecutive 57 DCM patients. There were 41 men and 16 women, whose mean age was 48 ys. (range 3-68 ys.). The mean LVEF in all patients was 29 +/- 11%, and the mean interval from the onset of symptom of cardiac failure (CHF history) was 4 ys. (range 0-33 ys.). With follow-up of 3.8 ys., five patients had died until the first year, and 14 had died until the third year. By using multivariate regression analysis, there were no prognostic significance in clinical parameters such as age, CHF history, sex, atrial fibrillation, except for NYHA class, and medication at the third year. In survival curves according to Kaplan-Meier method, RVEF and mean PA had predictive value (p less than 0.05), while LVEF did not. The patients with RVEF less than 45% had poor survival rate compared to those with RVEF greater than or equal to 45%. The patients with RVEF less than 45% showed lower LVEF and LVESVI. RVEF may offer prognostic predictive value through the effect of not only mean PA but also left ventricular parameter. In conclusion, radionuclide assessment of right ventricular function should be valuable for the prognostic evaluation of DCM patients.