In the present study, Listeria monocytogenes BCRC 14846 and Salmonella Typhimurium BCRC 10747 were subjected to acid adaptation at pH 5.5 at 37°C for 1 and 4 h, respectively. The viability of the acid-adapted cells of test organisms exposed to Clidox-S, a chlorine-containing disinfectant, and Quatricide, a quaternary ammonium compound, was examined and compared with that of the control cells at 25°C and 40°C. Results revealed that acid adaptation significantly enhanced the viability of L. monocytogenes and Salmonella Typhimurium exposed to the disinfectants under investigation. Both pathogens examined were more susceptible to Clidox-S and Quatricide at 40°C than at 25°C. Further, L. monocytogenes was more susceptible to Quatricide than Salmonella Typhimurium, whereas Salmonella Typhimurium was more susceptible to Clidox-S than L. monocytogenes.