A 32-year-old man was admitted to our hospital suffering from cough and bloody sputum. After the preoperative examination, the most suspected diagnosis was either a cardiac myxoma or a pulmonary embolism. At operation, the cavity of main pulmonary trunk was occupied with a tumor growing through the stalk from the outflow tract of right ventricle. The invasive tumor was not completely removed from the pulmonary tract. Rhabdomyosarcoma originating from the right ventricle was confirmed histologically. The patient died on the 199th postoperative day. A necropsy was not conducted. Diagnosis, operative indication and chemotherapy of cardiac rhabdomyosarcoma are discussed in this paper.