The association of optic glioma with von Recklinghausen neurofibromatosis (NF) is well established. However, the incidence of these tumors in a large population of NF patients, prospectively evaluated with modern radiologic techniques, has not been established. We investigated the ophthalmic and intracranial features of NF in 217 patients aged 4 weeks to 69 years, in whom the diagnosis was based on stringent criteria. Tumors at various locations along the anterior visual pathway occurred in 15% of patients and were occasionally bilateral. The mean age of patients with chiasmal tumors was approximately 15 years less than patients with tumors of the optic nerve only. Two-thirds (67%) of all tumors were neither suspected historically nor detected by ophthalmologic examination. Neither the ophthalmoscopic absence of optic atrophy nor the normal results of roentgenograms of the optic foramina were reliable predictors of tumors detected by CT scan. The presence of optic glioma is not correlated to other ocular, skeletal, neurologic, or anamnestic risk factors.