It is well documented that children with neurofibromatosis type 1 are at high risk for a variety of cognitive and learning deficits. The current study investigated the use of a developmental screening tool, the Parents' Evaluation of Developmental Status: Developmental Milestones, as an accurate, reliable, and efficient indicator of developmental delays. Sixty-eight percent of children with neurofibromatosis type 1 were found to have a developmental delay in at least 1 of the 8 areas tested by the Parents' Evaluation of Developmental Status: Developmental Milestones. Significant developmental abnormalities were found in the areas of fine motor (35%), gross motor (52%), and math/premath (31%). A positive association was found between the presence of a previously diagnosed optic glioma and math/premath delays (χ(2) = 0.0022) and between male sex and fine motor delays (χ(2) = 0.0325). The Parents' Evaluation of Developmental Status: Developmental Milestones assessment demonstrates the high presence of developmental delays in children with neurofibromatosis type 1 and the need for aggressive and early screening.