The surface of sheets of polyethylene was studied by means of a scanning electron microscope in order to compare the effects of corona discharges and those of the constituents of the discharge, i.e., uv radiation and electrons and O+ions of low energy. The deterioration produced by the O+ions resembles that produced by the discharge, and the deterioration produced by the electrons and the uv radiation does not. This difference tends to confirm infrared results and the assumption that the ions concentrated at the tip of a discharge erode the surface of the insulating material.