A 61-year-old male patient with a mass of lymph nodes on the left supraclavicular fossa was transferred to this institution in November, 1993, for further examination and treatment of possibly malignant tumors. Specimens of the mass obtained by direct biopsy from the left supraclavicular fossa indicated malignant lymphoma (ML) of histologically diffuse, middle cell type of B cell origin. Systolic ejection murmur (Levine 3/6) was auscultated over the left parasternal precordial area at time of admission. ECG revealed CRBBB and negative T wave in the a VL and V1-V5 leads. Echocardiography was performed because ECG abnormalities suggested possible invasion of ML to the heart. Large abnormal masses in the pericardium that had invaded the right ventricular cavity through the anterior wall of the right ventricle were present in the right ventricle (RV). The masses appeared to divide the right ventricular cavity into two parts, and there was mid-RV obstruction. ML was judged to be in stage IV. The mass disappeared entirely after two courses of therapy with CHOP-GCSF. Clinical diagnosis of the metastatic ML of the heart in vivo is rare. The value of this case results form our having observed the process of disappearance of the masses after effective chemotherapy. Our findings suggest that echocardiography may be useful in evaluating the healing stage of ML.