Children arriving at the emergency department with fever is a fairly common problem in pediatric practice and the pediatrician has to detect the minority of those children with severe bacterial infection. Rapid diagnosis and treatment of these severe infections is essential since a delay in the management may lead to poorer outcome. The inflammatory markers: procalcitonin and C-reactive protein are reliable markers of severe bacterial infections such as bacteremia, meningitis, pyelonephritis and bacterial pneumonia. We created a score utilizing both procalcitonin and C-reactive protein. This Lab-score has been tested and validated as the best marker of severe bacterial infections in children with fever without a source.