The stability of dislocation microstructure subject to cyclic softening is important in view of the phenomena of cyclic softening of materials subject to tensile or compressive prestrain which was reported by Coffin and Travernelli and investigated extensively by Feltner and Laird. Thus it is of interest to consider the detailed microstructural changes which accompany cyclic softening and to attempt to provide a quantitative description of the kinetics of softening. The present investigation has been concerned with the cyclic softening of low carbon iron (decarburized ferrovac E and Armco iron) which had been prestrained at 195 degree , 298 degree and 473 degree K in order to vary the dislocation arrangements before starting the cyclic straining. The model presented gives a preliminary account of the kinetics of cyclic softening and illustrates that the rate of softening is dependent on the initial dislocation distribution. The present data suggests that in order to inhibit the cyclic softening process some form of effective pinning of the prestrain dislocation substructure must be utilized as in the dynamic strain aging and thermal mechanism working procedures reported by Brown and Embury.