Neurofibromatosis type 1 (NF1) is a clinically diagnosed autosomal dominant disorder requiring routine clinical management, particularly during the pediatric years. An overlapping disorder, Legius syndrome, at times is clinically indistinguishable from NF1 and results in a small percentage of individuals being mischaracterized. Distinguishing these two entities is increasingly important for prognosis, reproductive planning, and clinical management. The goal of our study was to evaluate the cost impact of genetic testing for patients with solely pigmentary findings. The costs of genetic testing in patients aged 1.5–18 years were modeled using a simulated population, assuming the clinical management approach of a single NF1 clinic. Two genetic testing algorithms (SPRED1 testing alone, and NF1 mutation analysis with reflex to SPRED1) were compared against a baseline of no genetic testing. The cost for SPRED1 mutation analysis for each individual meeting NF1 diagnostic criteria without neoplastic or boney manifestation, when compared to the no-testing approach with routine follow-up mutations between the ages of 10 and 14 years, was minimal (range of $4–$16). Based on the clinical practice of one NF1 clinic, we found that the cost difference to perform SPRED1 mutation analysis on individuals who meet diagnostic criteria for NF1 without neoplastic or boney manifestation were minimal. Therefore it is important that “when to test decisions” remain a physician/patient discussion, as individual benefits may be greatest at a different age than when it is most cost efficient. © 2013 Wiley Periodicals, Inc.