Inappropriately prescribing antibiotics for non-bacterial infections remains common in outpatient settings despite the associated risks. This analysis of antibiotics prescribed to more than 2.8 million children showed more than 30% of children with bacterial infection, and 4%-70% of children with viral infection were inappropriately prescribed antibiotics. Inappropriate prescribing led to increased risk of adverse drug events (e.g., allergic reaction) and increased health expenditures in the following 30 days.