The addition of lithium chloride (LiCl) to a solution of polystyryllithium (PStLi) in tetrahydropyran (THP) reduces the rate of propagation of PStLi at a low concentration of the latter but accelerates it at higher concentrations of PStLi. Moreover, the addition of LiCl, which is dimeric in ethereal solutions, increases the conductance of PStLi solutions in tetrahydrofuran (THF) and THP to a much greater extent than expected from the separate conductances of PStLi and LiCl. which is itself even less dissociated than PStLi. These phenomena are fully explained by the dual action of LiCl. Below a certain concentration of PStLi, the dissociation, not of LiCl as such, as claimed before, but of its solvated dimer into free Li+ ions and ClLiCl triple ions provides Li+ ions that repress the ionic dissociation of PStLi by a common ion effect. This, in turn, diminishes the concentration of free polystyryl anions, which are the dominating species responsible for the propagation of PStLi, resulting in retardation. However, at higher concentrations of PStLi, Li+ ions produced by its dissociation are scavenged by the scavenging action of LiCl diniers, producing quintuple cations. This reduces the concentration of free Li+ ions and, therefore, increases the concentration of the reactive free polystyryl anions, resulting in an acceleration of the propagation.