Persistent fever or FUO (fever of unknown origin) is defined by a fever of more than 1‑2 weeks that remains unexplained, after considerable diagnostic efforts. In the travelling child, in addition to cosmopolitan infectious diseases, tropical pathogens must absolutely be considered according to the regions visited and the activities practiced. A detailed history and a complete clinical examination are essential to decide which supplementary investigations will complete the basic assessment, which must contain the search for malaria in any child who has visited an endemic area. Following the diagnostic strategy proposed in this article, the clinician should be able to diagnose the most common diseases.