Electrospray ionization mass spectrometry was performed to identify the structure of polymeric methyl acrylates generated via the cumyl dithiobenzoate (CDB), cumyl p-fluorodithiobenzoate (CPFDB), and 1-phenylethyl dithiobenzoate (PEDB) mediated reversible addition-fragmentation chain-transfer (RAFT) polymerizations. The relatively simple spectra clearly demonstrate the end groups of this living free-radical polymerization technique. Only polymeric chains carrying one leaving group of the RAFT agent and the dithiobenzoate end group as the active RAFT center were discovered. Multiple-stage mass spectrometric experiments and oxidation of the dithioester end group confirmed the structure of the generated polymers.