The epidermal nevus syndrome refers to the association of any epidermal nevus with extracutaneous abnormalities. The most common extracutaneous abnormalities are neurologic, skeletal, and ocular, although other organs may also be involved. Widespread use of magnetic resonance imaging (MRI) has resulted in an increasing appreciation of the role of cortical malformations in patients with neurological symptoms. Strokes and vascular abnormalities have been reported in patients with the epidermal nevus syndrome. Arteriovenous malformations and leptomeningeal angiomas have been found in some patients with the epidermal nevus syndrome. Generally, the diagnosis of an epidermal nevus is not in doubt. If there are any doubts, a skin biopsy should be obtained. Treatment of the nevus with dermabrasion, diathermy, laser treatment, and cryotherapy is associated with a fairly high risk of recurrence of the nevus. Focal resection of the epidermal nevus before puberty is advised because of the increased risk of tumor development.