Primary malignant neoplasms of the heart are very rare disorders, which are found at less 1/1000 necropsies. These malignancies are almost exclusively sarcomas and histologically assume a wide veriety of morphological subtypes, angiosarcomas, rhabdomysarcomas, and fibrosarcomas(or MFH) being the most frequent. We experienced a case in which left atrial myxoma was suspected by 2-D echocardigraphy and the histologic diagnosis of promary MFH was confirmed by operation. A 45-year old woman with primary MFH arising from posterior wall of left atrium, interatrial septum and mitral annulus is presented with a brief view of the literatures.