BACKGROUND: To determine the influence of chorioamnionitis and neonatal sepsis on procalcitonin (PCT) levels in very-low-birth-weight (VLBW) infants within the first week of life. DESIGN: PCT serum levels were measured in cord blood 1 h after delivery and on day 3 and day 7 of life. Chorioamnionitis and neonatal sepsis within the first week were monitored. RESULTS: Chorioamnionitis was present in eight of 37 patients (21.6%). PCT on day 3 was increased in both the "No chorioamnionitis" (2.54 ng mL(-1), SEM 0.51) and "Chorioamnionitis" (6.96 ng mL(-1), SEM 2.93) groups of VLBW infants compared with the 1st hour values (0.45 and 0.58 ng mL(-1) SEM 0.07 and 0.11, respectively, P < 0.001) of the same patients. The postnatal gain was higher in the "Chorioamnionitis" group (P < 0.01). Neonatal sepsis was diagnosed (after exclusion) in 12 of 32 patients (37.5%). Mean values of maximum PCT in patients with and without sepsis were 8.41 ng mL(-1) (SEM 1.87) and 3.02 ng mL(-1) (SEM 1.38), respectively (P