OBJECT: The diagnosis and treatment of Chiari malformation Type I (CM-I) has evolved over the last few decades. The authors present their surgical experience of over 2 decades of treating children with this form of hindbrain herniation. METHODS: The authors conducted a retrospective review of their institutional experience with the surgical treatment of the pediatric CM-I from 1989 to 2010. RESULTS: The 2 most common presentations were headache/neck pain (40%) and scoliosis (18%). Common associated diagnoses included neurofibromatosis Type 1 (5%) and idiopathic growth hormone deficiency (4.2%). Spine anomalies included scoliosis (18%), retroversion of the odontoid process (24%), Klippel-Feil anomaly (3%), and atlantooccipital fusion (8%). Approximately 3% of patients had a known family member with CM-I. Hydrocephalus was present in 48 patients (9.6%). Syringomyelia was present in 285 patients (57%), and at operation, 12% of patients with syringomyelia were found to have an arachnoid veil occluding the fourth ventricular outlet. Fifteen patients (3%) have undergone reoperation for continued symptoms or persistent large syringomyelia. The most likely symptoms and signs to resolve following surgery were Valsalva-induced headache and syringomyelia. The average hospital stay and "return to school" time were 3 and 12 days, respectively. The follow-up for this group ranged from 2 months to 15 years (mean 5 years). Complications occurred in 2.4% of cases; there was no mortality. No patient required acute return to the operating room, and no blood transfusions were performed. CONCLUSIONS: The authors believe this to be the largest reported series of surgically treated pediatric CM-I patients and hope that their experience will be of use to others who treat this surgical entity.