Human erythrocytes were irradiated in order to study the effect of x- rays on the cell membrane. The red blood cells were exposed to various dosages of 145KVP x-rays up to 10,000 R. The effect of the x-rays on the physical characteristics of the cell membrane was evaluated by use of an alternating current wheatstone bridge. Changes in the rates of ion transport through the membrane were evaluated by K42 tracer studies. The x-irradiation was found to have no detectable effect on the physical characteristics of the membrane, or upon the rate of uptake of potassium however, x-irradiation of 10,000 R was found to cause a substantial increase in the rate of potassium loss by the cells. These results are attributed to disturbance by the radiation of some intracellular process which is involved in the maintenance of the observed ionic concentration gradients.