Pediatric fever is a common complaint in children. The most common cause is self-limited viral infection. However, neonates and young infants are evaluated and treated differently than older, vaccinated, and clinically evaluable children. Neonates should be admitted to the hospital, young infants in the second month of life may be risk stratified, and those deemed low risk on testing may be sent home with close follow-up. Children older than 2 months may be evaluated clinically for signs of bacterial infection that require intervention. Urinary tract infections cause more than 90% of serious bacterial illness in children, and younger children have a higher incidence of infection.