We studied influences of mediastinal lymphadenopathy on cardiovascular system in nine cases of sarcoidosis with transesophageal ultrasonic endoscopy. Chest x-ray films revealed bilateral hilar lymphadenopathy in all cases, whose diagnoses were made histologically with biopsies of peripheral lung through flexible fiber optic bronchoscope and/or of lymph nodes. These findings were typical in this disease. Many compartments of cardiovascular system in mediastinal and hilar regions were visible with this technique in all subjects. And enlarged lymph nodes changed dimensions in these compartments, especially in main pulmonary arteries, left atria, pulmonary veins and aorta. Furthermore, these phenomena were seen in azygos vein and superior caval vein in some cases. It is suggested that these lymph nodes may influence hemodynamics in above-mentioned compartments of cardiovascular system, if this phenomenon deteriorates more progressively.