Background: The alveoli, the tiniest air sacs in the lungs, are particularly vulnerable to damage from the inflammation caused by pneumonia. For young children in the poor world, childhood community-acquired pneumonia (CAP) is the leading cause of death. CAP is an infection of the lower respiratory tract that spreads easily from person to person. The 116-amino-acid peptide procalcitonin (PCT) is the calcitonin precursor and has no known hormonal property. The levels of PCT in the serum of healthy people are either very low or undetectable. The inflammatory biomarker procalcitonin is of great importance. The CALC-I gene on chromosome 11 codes for a protein that serves as a precursor to calcitonin, a hormone that controls calcium levels in the body. Serum PCT levels may rise by a factor of 1000 due to induction by inflammatory cytokines and bacterial endotoxin in lung, liver, kidney, and adipose tissue during bacterial infections. In 2005, the FDA of the United States authorized PCT for use as a diagnostic tool for sepsis.  Objectives: Assessing the use of serum procalcitonin as a diagnostic and prognostic marker in children with pneumonia. Conclusion: procalcitonin should be considered as a useful diagnostic and prognostic biomarker in pediatric patients with pneumonia. It may have some utility in predicting the most severe outcomes.