In this study we aimed to analyze the diagnostic accuracy – both individually and in combination – of C-reactive protein (CRP), procalcitonin (PCT), white blood cell count (WBC), and neutrophil count (ANC), along with clinical findings, in predicting whether a young febrile infant has a viral infection, urinary tract infection (UTI) or serious bacterial infection (SBI). Here, CRP is linked to bacterial urinary tract infection.