OBJECTIVES: The objective of this retrospective claims database study was to better understand the burden of illness for pediatric patients in the US who have epilepsy with partial onset seizures and who are being treated with anti-epileptic drugs (AEDs). METHODS: Data were administrative claims from a large national US health plan. Patients were commercial enrollees ≥2 years and ≤17 years of age with ≥ 1pharmacy claim for an oral AED from 1/1/2006 – 11/30/2008; index date was defined as the first AED claim. Patients also had ≥ 1medical claim for epilepsy (ICD-9-CM 345.xx) during the 6 months pre-index period and were continuously enrolled 12 months post-index. RESULTS: Within commercially insured pediatric patients, 3,889 children met inclusion criteria; 54% were males; 59% were aged 2-11 years; and 51% lived in the southern US. The mean age of the population was 10.08 years. Overall, 77% had a Quan-Charlson comorbidity score of zero. Most frequently reported AHRQ comorbid conditions included epilepsy convulsions (100%), respiratory infections (66%), other nervous system disorders (43%) and headache (20%). Of 8 epilepsy-related risk factors examined patients experienced hyperkinetic syndrome (10%) and developmental disabilities (20%). Of 17 AED medications examined, the most prescribed overall were: oxcarbazepine (OXC) 21%; levetiracetam (LEV) 19%; valporate (VPA) 17%; lamotrigine (LTG) 17%; with least prescribed being gabapentin (GBP) at 1%. Their respective mean annual post-index pharmacy and total costs were: $5441 and $11,430, LTG; $3025 and $9121, LEV; $2095 and $5556, OXC; $1308 and $2807, VPA; and $917 and $1597, GBP. The overall post-index mean annual pharmacy costs were $2637 and mean annual total costs were $6813. CONCLUSIONS: Comorbid conditions associated with epilepsy are likely to contribute to the costs of pediatric epilepsy. Lamotrigine and Levetiracetam had the highest annual pharmacy costs compared to other drugs.