With applied dc electric fields in excess of 1.2 kV/mil, the current in iodine‐doped polyethylene is found to be no longer invariant with time, but to exhibit continuous oscillations superimposed upon a large background current. These oscillations appear at a well‐defined threshold field, which is found to be independent of temperature, but to depend on the concentration of iodine in the film. The frequency of the oscillations is very temperature dependent, having an activation energy of almost the same value as the conductivity. Increase of iodine concentration increases the frequency, but the frequency decreases with increase of field strength. The frequency is also found to be inversely proportional to film thickness. Transient response characteristics suggest that the formation of space‐charge regions may be important. The experimental results are compared with the theory of recombination waves in dielectrics, which considers the propagation of low‐field domains through the sample.