It was made a clinical-pathological study of six (6) cases of subacute sclerosing panencephalitis (SSPE) in order to demonstrate that the demyelinating process observed in this disease has its origin in the destruction of oligodendroglial cells by viral parasitism. As we know oligodendroglial cells are responsible for the myelination in the Central Nervous System. It was made a brief historical revision of the oligodendroglial cells concept and, after the description of the six cases, we tried to demonstrate that the demyelinating process observed are the result of oligodendroglial cells destruction.