In the last years, procalcitonin (PCT) has been proposed as an early marker of infections in newborns having registered different results. In this study, we aimed to investigate the value of serum procalcitonin for the diagnosis of sepsis in neonates and children procalcitonin in the diagnosis of neonatal sepsis and in children up to 1 year in the pathology of therespiratory system, gastrointestinal pathology, etc. At first, we established the clinical and paraclinical signs of systemic inflammation: increasing the temperature of the system, tachycardia, laboratory test: leukocytosis, C-reactive protein - for the diagnosis of sepsis.Some studies show that PCT gave a sensitivity between 83-100% and a specificity between 70-100% in early diagnosis of neonatal sepsis [1-7]; other researches question the accuracy of PCT in detecting neonatal sepsis.Procalcitonin (PCT) has been proposed as a marker of bacterial sepsis in critically ill patients. PCT is a precursor of calcitonin and a 116 amino acids protein. PCT levels more than 0.5 mg/dl are useful to determine the type of infectious process (bacterial or not).