To assess the natural history of optic pathway tumors (OPT) in children with neurofibromatosis type 1 (NF-1), from January 1985 through May 1993 we performed a prospective, longitudinal study of OPT in an unselected population of children with NF-1. Of 227 children with NF-1 seen in a specialty clinic, 176 (77%) underwent neuroimaging. Children in whom tumors were identified were followed closely by both repeated neuroimaging and ophthalmologic examinations to detect tumor growth or visual deterioration. Thirty-three children (19%) were found to have OPT at a median age of 4.2 years. The median age of children who had ophthalmologic complaints was significantly lower than that of children who had no such complaints (1.9 vs 5.3 years; p < 0.001). Although eight tumors were discovered because of ophthalmologic complaints or evidence of precocious puberty, 25 children (76%) were free of symptoms at the time of diagnosis. Twenty-one children (64%) had normal ophthalmologic findings at diagnosis; six children, all with chiasmal tumors, had previously unrecognized decreased visual acuity. Only three children (9%) had evidence of either tumor growth or deteriorating vision after diagnosis; the median duration of neuroimaging follow-up was 2.4 years (range, 0.2 to 7.2 years) and of ophthalmologic examinations 3.4 years (range, 0.2 to 8.1 years). All symptomatic OPT were diagnosed before 6 years of age. We conclude that OPT rarely progress during the next few years in children with NF-1 once the OPT have been discovered. The utility of screening neuroimaging for OPT in symptom-free children with NF-1 appears very limited.