Alexander's disease is a rare and poorly understood cause of progressive neurological deterioration. Although the clinical history depends on the age group involved, the histological character and distribution of lesions tend to be uniform. The pathological features argue strongly that Alexander's disease represents a nonneoplastic disease of astrocytes. Numerous questions remain unanswered, including the factors responsible for the severity of the illness in the infantile group and the mechanism of demyelination secondary to astrocytic dysfunction. This series of 6 patients with Alexander's disease represents a wide spectrum of ages, enabling the pathological and clinical abnormalities to be related to a postulated mechanism of astrocytic dysfunction.