Not uncommonly, during the course of a workup for fever, the pediatrician will find that a patient has neutropenia. Neutropenia is defined as an absolute decrease in the number of circulating neutrophils in the blood. The lower limit for normal neutrophil counts is 1000/mm3 in infants between 2 weeks and 1 year of age; after infancy the corresponding value is 1500/mm3. Blacks have lower neutrophil counts, and the lower limit is 100 to 200/mm3 less than those cited for whites. These lower counts probably reflect a relative decrease in the storage pool of the bone marrow.