The pressure does not change the amount of PO(4) permeating into the outer medium from blood erythrocytes. The amount of P(32) entrance into erythrocytes from the outer medium is equal to the control at 50-100 atm. pressure, probably increases 200-1000 atm. pressure. Particularly, the higher the pressure is, the more remarkable this effect is. The electric conductivity of the erythrocyte plasma membrane increases during and after the compression. The permeation of Cl into the medium from erythrocytes is augmented by pressure (200-1000 atm.). Summaring above, the permeability of the erythrocyte plasma membrane appears to increase at high pressure.