A 70-year-old woman was admitted with precordial pain. Two-dimensional echocardiography revealed a right atrial tumor. CT scan also showed a high density tumor in the right atrium. Right atriography demonstrated a mobile tumor with a stalk arising from the vicinity of the Eustachian valve. On open heart surgery the stalk of the tumor seen to be attached to the Eustachian valve. The tumor was very hard because of massive calcification. Removal of the tumor was accomplished in the standard fashion, excising the Eustachian valve together with surrounding endocardium to prevent recurrence. The weight of the tumor was 20g and the size was 6×3×2cm. Histologic examination of the tumor revealed myxoma. Thirty five cases of right atrial myxoma have been reported in Japan. There was only one previous report which reported a case originating from an Eustachian valve.