Wyburn-Mason's syndrome is a rare neurocutaneous disorder consisting mainly of unilateral arteriovenous malformations of the midbrain and retina with multiple cutaneous nevi. The authors report on the clinical presentation, neurologic phenotype, and long-term neurologic follow-up of two unrelated children. The first patient had recurrent epistaxis during early childhood. At the age of 7 years, he developed acute hemianopsia and right hemiplegia. Angiography revealed large bilateral arteriovenous malformations involving the midbrain thalamic area and the right optic nerve. During the following years, he had recurrent episodes of headache, right hemiplegia, and cognitive deterioration. The second patient had some episodes of epistaxis in the first years of life. At the age of 5 years, he presented with sudden onset of headache, followed by a loss of consciousness, vomiting, and, subsequently, visual disturbances. Angiography revealed deeply located arteriovenous malformations involving the right temporal, frontobasal, capsulonuclear, insular, and parietal areas and the right optic nerve. During the following years, he had an acute strokelike episode followed by transient hemiplegia and slow progressive signs, with mild worsening of cognitive abilities. Early onset of neurologic manifestations is a poor prognostic factor for long-term outcome.