An attempt has been made to determine the significance and outcome of optic atrophy as an apparently isolated entity in the pediatric age group. A follow-up study was made of 48 children who presented in early childhood with optic atrophy with no known cause and no obvious systemic or neurological disease. It was found that the prognosis for useful vision is in general favorable in this group of cases. However, the significant incidence of mental retardation and other neurological impairment was noted for those children who had manifested severely impaired vision under one year of age. There was no correlation between specific symptoms and the outcome of vision. The patients with idiopathic optic atrophy were compared with other patients who presented with optic atrophy without signs of systemic or neurological disease on initial examination but who were later found to have underlying disease. X-ray findings of enlargement of the optic foramina, deformity of the sella turcica, and suprasellar calcification or hyperostitic changes in the region of the optic foramen were found to be important differential diagnostic features, as was the presence of proptosis or visual field defects, reflecting involvement of the optic chiasm or retrochiasmal visual pathways. By the use of these features and certain laboratory determinations it was possible to separate the idiopathic group from patients whose optic atrophy was secondary to optic nerve and chiasm gliomas, other intracranial neoplasms, fibrous dysplasia, congenital syphilis, and orbital neurofibroma. Problems in the diagnosis and differential diagnosis of optic atrophy have been discussed.