This study was designed to assess the value of procalcitonin in establishing the diagnosis and evaluating the prognosis of neonatal sepsis. Thirty-four infants with neonatal sepsis were included in the study. Procalcitonin values of the cases with sepsis were (2.21 +/- 2.48 ng/ml) significantly higher than the values in the control group (0.71 +/- 0.5 ng/ml; p = 0.01). On the 7th day of therapy neonates who had achieved clinical recovery had a significant decrease of procalcitonin levels (0.55 +/- 0.27 ng/ml) compared to the initial values (p = 0.001). Initial mean procalcitonin levels of the cases resulting in death were 4.31 +/- 3.66 g/ml. This was significantly higher than the initial values of the patients who had clinical recovery (1.18 +/- 1.24 ng/ml;p = 0.02). Procalcitonin is a valuable marker for diagnosis, for evaluating prognosis and response to therapy in neonatal sepsis.