Fever is probably the most common reason for a child to be taken to a doctor’s surgery, with approximately 20 to 40% of parents reporting that their child had a febrile illness in the last year. Febrile illness in young children has a wide range of causes, and creates concern in parents and carers. In most cases, the cause is a self-limiting viral infection. However, fever may also be the presenting feature of serious bacterial infections such as meningitis. Infections remain the leading cause of death in children under the age of 5 years, despite advances in healthcare. Therefore, guidance to help healthcare professionals distinguish between the majority of children who have minor self-limiting conditions and the occasional child with a sinister or even life-threatening infection is vital. This article aims to advise GPs on how to assess and initially manage a febrile child younger than 5 years, principally based on up-to-date National Institute for Health and Care Excellence guidelines.