The Authors relate a clinical, laboratorial, eletroencephalografic and virological study of four patients with the clinical diagnosis of subacute sclerosing panencephalitis (SSPE). All four had high levels of anti-measles antibodies in the cerebrospinal fluid and in the blood, and in three of them the levls were higher in the cerebrospinal fluid. Cerebral biopsies were performed on two of these patients, showing a picture of chronic meningoencephalitis, with scattered foci of neurophagia and perivascular inflammatory infiltrates of lymphocytes and plasma cells. The Authors also review eighteen previously published cases, in order to analyse more fully the nature of the perivascular and meningeal inflammatory infiltratos. The histopathologic is of slight meningeal inflammatory reaction, which contrasts with the dense perivascular infiltrates of lymphocytes and plasma cells, which frequently present a great number of Russell bodies. In view of these findings, the Authors suggest that the anti-measles antibodies, which were found in such high concentrations in the cerebrospinal fluid, might be produced in the perivascular inflammatory infiltrates within the central nervous system.