Abstract
Mature granulocytes from six patients with myelocytic leukemia and monocytic cells from two patients with monocytic leukemia were damaged after incubation with leukocidin from Staphylococcus aureus. The immature granulocytes were not significantly affected. The lymphocytic cells from one patient with lymphocytic leukemia were not markedly damaged. The numbers of erythrocytes from all nine patients remained practically unchanged with lower concentrations of leukocidin.