ABSTRACT.The bacteriological and haematological features of 11 infants with early‐onset bacterial pneumonia (EBP) were compared with those of 45 infants with severe hyaline membrane disease (HMD) to determine the sensitivity and predictive value of these features for the diagnosis of EBP in the presence of severe respiratory distress. All infants with EBP had positive surface site gram stains, abnormal total neutrophil counts, and increased immature: total neutrophil ratios but these features were also present in 18%, 40% and 22%, respectively, of infants with HMD. However, when these three features were combined all infants with EBP were identified (sensitivity = 100%) and all but one infant with HMD were excluded (predictive value = 92%).The clinical and radiological features of EBP are nonspecific and all infants with respiratory distress should have surface site gram stains examined for bacteria. If these are positive, an abnormal total neutrophil count and an increased immature: total neutrophil ratio will distinguish EBP from HM