A simple technic for separation of human leukocytes is described. It utilizes differential sedimentation following red cell and platelet agglutination induced by Polybrene. In this technic, lymphocytes are partially removed and over 50 per cent of polymorphonuclears are recovered. The leukocyte/red cell ratio is about 5, if blood samples with normal leukocyte counts are used. By use of blood samples containing higher white cell counts this ratio may be increased. The separated cells proved to be highly viable as tested by phase microscopy, supravital staining and phagocytosis. There was no significant change in oxygen uptake of leukemic cells in the presence of a relatively large Polybrene concentration.