OBJECTIVES: To characterize the utilization of tumor necrosis factor-alpha inhibitors (TNFI) in children with juvenile idiopathic arthritis (JIA) and young adults with rheumatoid arthritis (RA).  METHODS: Patients with incident JIA or RA were identified using healthcare claims data from 2009 to 2013. TNFI utilization patterns were examined, including switching among TNFIs, adherence, persistence, and time from diagnosis to TNFI use. Earlier TNFI treatment without prior use of traditional disease-modifying antirheumatic drugs (DMARD) and use of specific TNFIs were analyzed by age group. RESULTS: Among 6,962 children and young adults with new diagnoses of JIA/RA, 43.5% were treated with DMARDs and 18.6% were treated with TNFIs. In these TNFI users, 39.1% received earlier TNFI therapy without prior use of DMARDs. Patients diagnosed in more recent years (2012 to 2013) had a higher instantaneous rate of receiving a TNFI (hazard ratio 1.13, 95%CI 1.00-1.28, p=0.044) than those in year 2009 to 2011. Etanercept was the most commonly used, especially by children aged <12 (75.5%) and adolescents aged 12 to 17 (62.5%), while adalimumab was more commonly prescribed for young adults aged 18-24 (35.0%) compared to children (16.4%) and adolescents (27.8%). Adherence measured as mean proportion of days covered ranged from 70.4% to 93.2% for individual TNFI agents. Only about 60% of patients continuously took TNFIs for 12 months. When switching occurred, switching from etanercept to adalimumab was the most common pattern. CONCLUSIONS: Earlier TNFI therapy was observed in 39.1% of children and young adults taking TNFIs. In addition, the time to first TNFI prescription became shorter over the study period. Future research should evaluate the long-term effectiveness and safety of this more aggressive TNFI therapy.