In this paper we report on the time behavior of the apparent pitch of a cholesteric mixture undergoing a step‐like dc electric field applied parallel to the helical axis. We show that the relative variation of the apparent pitch &Dgr;&lgr;(t)/&lgr;0decreases from the initial value to negative ones (&lgr;<&lgr;0) by two different characteristic times and tends finally to a saturation value with &Dgr;&lgr;/&lgr;0<0 after a long time. An attempt to explain this phenomenon in a (semi‐)quantitative way has been made by considering relaxation mechanisms on different spatial scales. ©1995 American Institute of Physics.