The management of infants and young children with fever without source (FWS) is a difficult challenge for pediatricians. Of 100 children with FWS, ten to 20 will have a serious bacterial infection (SBI) and 4 to 5% bacteriemia. Because no single aspect of the medical history, physical examination and laboratory parameters can reliably identify a child at increased risk for SBI, most management strategies now focus on identifying infants that are less likely to have SBI. The negative predictive value for 'low-risk criteria' SBI is close to 100%. Therefore, if it is possible to carry out a daily clinical examination, antibiotic treatment can be withheld from these children. For children who do not fulfill the low-risk criteria, antibiotics must be administered until the results of blood and urine samples and possibly CSF cultures have been obtained.