Subpial and subependymal gliosis with abundant Rosenthal fiber (RF) formation are described in two patients. In one, the process appeared as a narrow band over the entire neuraxis and was not accompanied by neurologic manifestations. In the other, the changes were mostly restricted to the lower medulla and upper cervical cord and displayed invasive features. The glial proliferation with RF in the second patient was associated with an inflammatory component, dense collagen deposition, perivascular Schwannosis and demyelination. Involvement of some of the medullary nuclei and their tracts may explain the patient's vague bulbar symptomatology. The underlying cause which led to astrocytic proliferation with excessive RF in these two patients remains elusive. Possible factors contributing to this phenomenon are discussed in the context of Alexander's disease.