Intermittent fever is rare during the course of infectious diseases but it represents a diagnostic and therapeutic challenge. The most frequent infectious causes of intermittent fever are focal bacterial infections, mainly infections localised to canals like urinary or biliary ducts or the colon and also infections of a foreign material. Other causes are less frequent, like infective endocarditis, tuberculosis, infections due to Yersinia enterocolitica or malaria, or exceptional like borreliosis, ratbite fever, chronic meningococcemia or chronic Epstein-Barr Virus infection. Careful anamnesis and clinical examination as well as a few simple complementary investigations, preferably performed during a febrile episode, are often sufficient to set the limits of possible further more complex investigations.