An analysis of moving dissociated dislocations subjected to both a quasi-static viscous friction force and a periodic lattice resistance is performed: Metastable configurations are expected, the range of the dissociation distances being asymmetrically distributed with respect to the equilibrium dissociation distance. The data of earlier investigations on the influence of high external stress on the dissociation of dislocations in silicon and germanium, as determined by transmission electron microscopy, are re-examined. It is shown that in most cases the range of observed dissociation widths is consistent with the predictions of the model