The epidermal nevus syndrome is a neurocutaneous disorder characterized by distinctive skin lesions and often serious somatic and central nervous system (CNS) abnormalities. We observed four cases of this disorder with epidermal nevi and neurologic manifestations, including mental retardation, seizures, ophthalmologic abnormalities, intracranial aneurysm, and porencephalic cyst. A review of 60 reported cases of the epidermal syndrome and our experience suggest that CNS complications are more likely to be associated with epidermal nevi on the head and that the CNS abnormalities are most often ipsilateral to the skin lesion.