This article discusses the management of children under the age of five who present to nurses in primary or out-of-hours care with fever. The approach to assessment of these children is discussed, using the National Institute for Health and Clinical Excellence guidelines on the management of children with fever as a basis for logical and evidence-based care. Dealing with uncertainty in cases presenting some risk factors for serious disease and uncertainty in diagnosis are examined, and consideration is given to how to manage this risk as safely as possible using case studies.