Radionuclide cardioangiography has been widily applied and has played mjor foles in moninvasive assessment of cardiac function. Three techinques, first-pass gated first and gated equlibrium nethods have commonly been used to evaluate right ventricular ejection fraction which usually abnormal in the patients with cardiopulmonary disease. It has been known that the gated first pass method is most accrate method among the three rechiques in assessment of fight ventricuiar ejection fraction. The radionuclide right ventricular ejection fraction values were determined in 13 normal subjects and in 15 patients with chronic obstructive puimonary disease by the gated first pass method and compared with those of the first pass method because there has been no published data of fight ejection fraction by the gated first pass method were compared with the detas from the pulmonary function test performed in the patients wih chronic obstructive pulmomar desease. The results were as follows; 1) The values of fight ventricular ejection fraction by the gated first pass method were 50.1 +- 6.1% in normal subjects and 38.5 +- 8.5 in the patients with chronic obstructive pulmonary disease. There was statistically significant difference between the right ventricular ejection fraction of each of the two groups (p<0.05) 2) The right ventricular ejection fraction by the gted first pass method was not linearly correlated ith FEV, VC. DLCO. and FVC as well as PO2 and PCO2 of the patients with chronic obstructive pulmonary disease. We concluded that right ventricular ejection fraction by the gated first pass method usingradionuclide cardioangiography may be suseful in clinical assessment of the right ventricular function.