NEUTROPHILS in the blood of patients with infection frequently show degenerative changes including degranulation, swelling, pyknosis, toxic granulation, and vacuolization.1,2 It has been suggested that the extent of these alterations in the cell reflect the severity of disease in the patient.3 We have been impressed that vacuolization of the cytoplasm, in particular, is correlated with septicemia, and that examination of the peripheral blood may lead to the diagnosis of septicemia prior to bacteriologic confirmation. This report describes a prospective study designed to test this correlation. Materials and Methods Wright-stained smears of undiluted capillary blood were examined by technicians of the hematology laboratory on routine request from the ward physicians. The presence or absence of vacuolization of the cytoplasm of the neutrophils was noted during the course of a differential count of 100 leukocytes. The technicians were unaware of the clinical diagnosis. Results Approximately 3,500 smears were examined. Of