OBJECTIVE: To study the changes of serum procalcitonin (PCT) in neonates with sepsis. METHODS: Serum PCT was determined using an immunoradiometric assay in 20 newborn infants with neonatal sepsis, 24 neonates with hypoxicischemic encephalopathy (HIE) and 16 healthy newborn controls. RESULTS: Increased levels of serum PCT were found in neonates with sepsis compared with the control group ［(112.23±10.13) μg/L vs (8.65±2.14) μg/L］, (P<0.01). After 1 week of treatment with appropriate antibiotics, PCT levels returned to normal. There was no difference between HIE neonates and the control group. CONCLUSIONS: Elevated serum PCT levels are noted in neonatal sepsis. PCT might be of value in the diagnosis of neonatal sepsis.