The clinical, laboratorial and radiological features of a 3-month-old child with neurocutaneous melanosis are described. The patient was born with multiple disseminated benign cutaneous nevi, proven by skin-biopsy, and presented with drug-resistant seizures and psycho-motor retardation. Serial cerebrospinal fluid studies showed high protein and low glucose levels, with pleocytosis and malignant cells in the fluid. Pneumoencephalogram showed mild non-obstructive hydrocephalus. Immunological studies showed normal immunological activity at three months of age and very poor activity at one year. The patient died at 16 months of age, after the sudden onset of intracranial hypertension and meningeal signs. Immunotherapy and chemotherapy were suggested but not accepted by the family. Some comments are made based on this and other 43 cases described in the literature; the value of laboratory studies in detecting malignant transformation in the meninges in patients with benign skin nevi is stressed.