To determine the usefulness of neutrophil values in diagnosing neonatal sepsis among infants at risk of neutropenia, we evaluated the pattern of sequential absolute total and immature neutrophil counts and the immature to total neutrophil (I:T) proportion over the first 5 days of life in infants with sepsis (n = 13), asphyxia neonatorum (n = 12), or delivered of mothers with pregnancy-induced hypertension (PIH) (n = 20), comparing values to references ranges previously reported by us. Neutropenia was initially present in 67% and 50% of infants with asphyxia and those whose mothers had PIH, respectively, and persisted through the first 3 postnatal days. In contrast, infants with sepsis were less likely to be neutropenic initially (38%), and neutropenia did not persist after 36 hours of age. Elevated values for the total immature neutrophil count and I:T proportion were much more likely to occur in infants with sepsis (46% and 61%, respectively) than in infants of mothers with PIH (4% and 12%) or those with asphyxia (13% and 22%). The importance of considering the perinatal history as well as the differential neutrophil count in the evaluation of neonatal neutropenia is demonstrated.