The serum concentration of protein C reactive (PCR) in preterm and term children was assessed on the first, fifth, eighth and fifteenth day of life. The data obtained show that in all cases characterised by PCR values higher than 10 mg/l on the first day of life a serious infectious pathology was present which required antibiotic treatment, monitored by subsequent PCR samplings. In all cases in which PCR was negative on the first day of life and in later samples, none had presented infectious pathologies. Analysis of the results showed that so-called borderline values (greater than 2 mg/l less than 10 mg/l) were present in some newborns at risk for the development of infectious pathologies. These children were subjected to antibiotic therapy as prophylaxis and in subsequent samples PCR became totally negative.