OBJECTIVES: Infants who have a fever with no obvious source of infection present a diagnostic dilemma. A  significant number of these patients may have a serious bacterial infection; making proper diagnosis and management important. Physical examination do not always identify patients with serious bacterial infection (SBI). If SBI are not recognized promptly can cause significant morbidity or mortality. The aim of this study was to determine the cost-effectiveness of 4 different screening strategies of Serious Bacterial Infections (SBI) in Children Presenting with Fever without Source (FWS) in Argentina METHODS: : A decision tree was designed to model a hypothetical cohort of 10,000 children with FWS. We compared the incremental cost-effectiveness of four strategies to detect SBI (Rochester criteria (RC), RC+ procalcitonin (PCT) , RC + C reactive protein (PCR) and no tests (NT).The analysis perspective was that of health-care payers, and we calculated only the direct medical costs.We conducted sensitivity analyses with Monte-Carlo simulation method to understand the key drivers and general sensitivity of the model. RESULTS: ER+PCR result in US$ 784 per correctly diagnosed cases of SBI versus US$ 839 of ER+ PCT, US$ 1116 de NT or US$1193 de ER. The sensitivity analysis shows if the probability of IBS is equal or less than 14% the strategy of choice is NT CONCLUSIONS: RC+PCR is the strategy more cost- effective to detect SBI in children with Fever without Source in Argentina. When probability of IBS is equal or less than 14% the strategy of choice is NT.