One-hundred sixty children under the age of 6 years presented for diagnostic evaluation regarding neurofibromatosis-1 (NF-1). Using the National Institutes of Health Consensus Conference criteria, 151 (94%) of the children were classified on initial examination: 112 were diagnosed as having NF-1 and 39 were found to be unaffected (all 39 have remained asymptomatic on follow-up). Nine could not be classified (3 have subsequently met minimal diagnostic criteria on follow-up). Clinical manifestations of NF-1 include cafe au lait spots (97%), freckling in the axillary or inguinal region (81%), Lisch nodules (30%), neurofibromas (15%), pseudoarthrosis (6%), and optic nerve gliomas (4%). More than minimal diagnostic criteria were met by 80% of the children who had a positive family history and by 32% of those who did not. Thus, the clinical diagnosis of NF-1 is possible in the child who is under 6 years of age, and the National Institutes of Health criteria are useful and applicable.