A 27 year-old female patient was admitted to our hospital because of right cervical tumor. Physical examinations revealed right and left cervical lymphadenopathy. A roentgenogram of the chest disclosed a right anterior superior mediastinal mass. From the histological examination of right cervical lymph node biopsy specimen, she was diagnosed as having Hodgkin's disease of nodular sclerosis. From the findings of ⁶⁷Ga-scintigram, ²⁰¹Tl-scintigram and lymphangiography, she was considered to be at the clinical stage II-A. Thirty nine days after initiation of mantle field radiation therapy, when 3,060 rad had been delivered to the tumor area, she had an episode consisting of disturbance of consciousness, precordial oppression, cyanosis, tremor and weakness of extremities. ECG revealed T wave inversions in leads V₃ and V₄ and depressions of ST segment in leads I, II, aV_F, V₅ and V₆. Other examinations revealed no abnormalities. The symptoms disappeared about three weeks later and the radiation therapy was completed without the recurrence of the cardiovascular symptoms. The deeply inverted T waves in leads V₁ and V₂, however, remained even at the termination of the radiation therapy. The symptoms and ECG changes were thought to have been induced by the irradiation.