1. The drumstick and other nuclear appendages of the nuclei of polymorphonuclear neutrophils from patients with chronic granulocytic leukemia (CGL), leukemoid reactions and inflammatory leukocytoses were studied.
2. The drumstick counts of the leukocytes of patients with CGL were abnormally low. In contrast, the counts in the leukocytes from patients with the other disorders were not reduced. The low counts increased rapidly in response to treatment and were maintained at normal levels during remission.
3. The normalization of drumstick counts in CGL paralleled the leukocyte alkaline phosphatase and catalase concentrations.
4. The number of sessile nodules and small clubs in each of the disorders studied was moderately reduced. Following treatment, the counts returned to normal. This suggests a relationship between the development of these appendages and hyperproliferation of neutrophils.