The transient, excess source‐drain current which occurs under freeze‐out conditions when a metal‐oxide‐semiconductor field‐effect transistor (MOSFET) is switched into a conducting state is described. The major features of the observed transient response forn‐channel MOSFET’s in the temperature range 10–25 °K are explained in terms of a simple one‐dimensional model. The transient response is largely independent of both temperature (in this range) and the static current level, except for the variation of relaxation rate with temperature. The transient response waveform and the temperature dependence of the relaxation rate forn‐channel MOSFET’s differ greatly from previously reported results onp‐channel MOSFET’s.