Object. Endoscopic third ventriculostomy (ETV) is an alternative to ventriculoperitoneal shunting for hydrocephalus treatment. Choice of treatment options raises questions about which patients are likely to benefit from ETV. The authors performed a population-based analysis using an administrative claims database, examining current practice and outcomes for pediatric patients in the US. Methods. The authors queried the MarketScan (Truven Health Analytics) database for Current Procedural Terminology codes corresponding to ETV and ventriculoperitoneal shunting from 2003 to 2011; they included patients 19 years or younger and extracted data from initial and subsequent hospitalizations. Hydrocephalus etiology was classified with ICD-9-CM coding. ETV failure was defined as any subsequent ETV or shunt procedure. Results. Five hundred one patients underwent ETV. Of these, 46% were female. The mean age was 8.7 ± 6.4 years (± SD). The mean follow-up was 1.9 ± 1.8 years. Etiology of hydrocephalus was primarily tumor (41.7%) and congenital/aqueductal stenosis (24.4%). ETV was successful in 354 patients (71%). The mean time to failure was 109.9 ± 233 days. Of the 147 patients with ETV failure, 35 (24%) underwent repeat ETV and 112 (76%) had shunt placement. Patients in age groups 0 to < 6 months and 6 months to < 1 year had a significantly higher rate of ETV failure than those 10-19 years (HR 2.9, p = 0.05; and HR 2.3, p = 0.001, respectively). History of prior shunt was associated with higher risk of failure (HR 2.5, p < 0.001). There were no significant associations between hydrocephalus etiology and risk of failure. A second wave of failures occurred at 2.5-3.5 years postoperative in tumor and congenital/aqueductal stenosis patients; this was not observed in other etiology groups. Conclusions. This study represents a cross-section of nationwide ETV practice over 9 years. ETV success was more likely among children 1 year and older and those with no history of prior shunt.