The C‐reactive protein (CRP) concentration was determined in 25 infants whose mothers had presented with prolonged rupture of amniotic membranes (PROM) and/or amnionitis. CRP was positive (i.e ≥ 6 mg/1) within the first 6 hrs of life in 10 and negative in 15 infants. Clinically, all infants with positive CRP developed symptoms suggesting bacterial infection and both the absolute immature neutrophil counts as well as the ratio immature/total neutrophils were significantly higher in them on day 2 of life than in infants with negative CRP. Blood cultures were only positive in infants with positive CRP. Thus CRP can be regarded as an early marker for neonatal bacterial infection due to PROM and/or amnionitis.