Dilute solutions of unimodal high-molecular-weight poly(butyl cyanoacrylate) (''parent'' polymer) in tetrahydrofuran (THF) at 21 degrees C underwent rapid depolymerization accompanied by simultaneous repolymerization of the unzipped monomer to yield lower-molecular-weight ''daughter'' polymer following addition of tetrabutylammonium hydroxide (TBAOH), a slow initiator of butyl cyanoacrylate (BCA) monomer. The rate-determining step for the reaction was tentatively identified as abstraction of the terminal chain proton. Similarly, addition of TBAOH to a THF solution of BCA monomer resulted in initial formation of high-molecular-weight (MW) polymer that subsequently rapidly depolymerized with simultaneous formation of TBAOH initiated, low-MW daughter polymer. The depolymerization-repolymerization reaction is the relaxation process that occurs following perturbation of the monomer/high-MW parent polymer equilibrium by low-MW daughter polymer and proceeds at least 100 degrees C below the ceiling temperature of the parent polymer.