Two unusual cases of neurocutaneous melanosis are presented. Both patients had congenital giant hairy nevi and both developed hydrocephalus, seizures, and myelopathy. The first patient displayed multicentric cerebral and spinal cord melanosis, as opposed to the more commonly described basilar leptomeningeal involvement. The second patient had total spinal leptomeningeal involvement, and ventriculoperitoneal shunting for hydrocephalus produced peritoneal metastasis of melanoma. An individual born with a congenital giant hairy nevus or marked generalized cutaneous pigmentation should be closely observed for the development of malignant melanoma of the nervous system.