Abstract.Human red cells, granulocytes and lymphocytes were examined electro‐phoretically. The effect of change of pH and ionic strength of the medium was determined. Lowering the ionic strength had the effect, not only of altering the electrophoretic mobility but also the characteristic shape of the pH mobility curves. Antilymphocyte globulin was shown to modify the mobility of granulocytes and lymphocytes, the latter to a greater extent. The results when compared to a silica surface completely covered with horse antihuman lymphocyte globulin show that the lymphocyte is only partially covered, suggesting a relatively low number of antigenic sites on the surfac