A relatively rare case of malignant lymphoma of the brain was reported. A 64-year-old male was admitted to our hospital, October 2, 1976, complaining of right hemiparesis and expressive aphasia. Neurological and radiological examinations revealed a huge space-occupying lesion in the left frontoparietal region. An external decompressive surgery and biopsy were performed. The excised specimens was diagnosed as malignant lymphoma (lymphosarcoma type) histologically. Radiation (5000 rad of 60Co) and chemotherapy with anticancer drugs were carried out after the operation. The patient, however, died at seven months after the onset. On necropsy the tumor was infiltrated extensively in the left frontal, parietal, temporal and occipital lobes, but extended not to the thalamus, basal ganglia and ventricular system. This case was suggested primary malignant lymphoma of the brain, according to the physical and radiological examinations of the whole body, although the autopsy was performed only about the brain. The nomenclature, clinicopathological and immunological problems of malignant lymphomas of the nervous system were also discussed, reviewing the previously reported cases.