A series of 200 patients operated on at the Rome University Neurosurgical Clinic for primary glioblastoma is analyzed. Eight of these patients (4%) survived for over four years. The histological preparations showed more or less heavy perivascular lymphocytic infiltration in six of these cases. Since such infiltrations in malignant tumours of other organs are recognized as having an immune function, expressing the host's resistance to his tumour, the longer survival of the cases considered may well denote an immune defensive mechanism.