The central nervous system (CNS) findings associated with congenital hypomyelinating polyneuropathy (CHN) are not established due to a paucity of reported post-mortem examinations. In this report we describe the pathologic changes found in the peripheral nervous system and CNS in a 2 1/2-week-old infant with a clinical diagnosis of CHN who died of respiratory failure clinically attributed to phrenic nerve dysfunction. Macroscopic findings included striking hypoplasia of the corpus callosum and anterior commissure, cerebellum, crus cerebri, ventral pons and pyramids. Histologic and immunohistochemical findings included complete absence of myelin staining and myelin basic protein immunoreactivity (MBP-IR) in the cerebral hemispheres, cerebellum, brainstem, cranial nerves and spinal cord despite little or no detectable reduction in numbers of oligodendrocytes. A severe fibrillary astrocytosis was seen at each of these sites. A slight reduction in neurons was identified in the cerebellum and spinal cord but nowhere else in the brain. These findings raise the possibility that deficient or markedly delayed CNS myelination accompanies peripheral hypomyelination in some cases of CHN.