1. The average values and the range of drumstick counts in the neutrophil granulocytes in males and females of a normal group of rhesus monkeys were estimated.
2. No important individual differences in counting were found between two groups of workers.
3. Irradiation and treatment with autologous bone marrow does not influence the drumstick appendage frequency.
4. The drumstick counts are an important indication of the take of a bone marrow graft when female donors and male hosts are used.