Although an association between optic glioma and neurofibromatosis is well recognized, there has been no previous analysis of cases relating the locus of tumor to the presence or absence of von Recklinghausen's disease. This paper presents the results of such an analysis as well as a description of the comparative histology of optic gliomas in patients with and without neurofibromatosis. We conclude that optic gliomas in patients with neurofibromatosis present preferentially as multicentric lesions or as lesions affecting the optic nerve alone without invasion of the chiasm, that these tumors frequently differ morphologically, and that patients with neurofibromatosis and optic glioma may have a clinical course different from that of patients with optic glioma unassociated with neurofibromatosis. Previously published reports are reviewed in light of these observations.