Benzoic and stearic acids are shown to react with 2-bisbenzothiazole-2,2'-disulfide (MBTS) and its polysulfides (MBTP) at vulcanization temperatures to form acid-accelerator complexes 2-benzoylthiobenzothiazole (BzM) and stearicthiobenzothiazole (StM), respectively. At higher temperatures MBTS, MBTP, BzM, and StM are decomposed by the acids. Analogous reactions are observed with tetramethylthiuram disulfide (TMTD) and its polysulfides (TMTP). Lesser amounts of acid-accelerator complexes 2-benzoyldimethyldithiocambamate and stearicdimethyldithiocarbamate are formed, but TMTP are more susceptable to decomposition at higher temperatures. The destruction of MBTP and TMTP by carboxylic acids will reduce the concentration of accelerator polysulfides available in compounds, and should impact negatively on vulcanization.