Previous unpublished experimental results of fractional factorial experiments showed that significant external factors affecting high-pressure processing (HPP) inactivation were pressure, temperature, and pressure holding time. Based on these results, response surface methodology (RSM) was employed in the present work, and a quadratic equation for HPP inactivation was built with RSM. By analyzing response surface plots and their corresponding contour plots and by solving the quadratic equation, experimental values were shown to be significantly in good agreement with predicted values, since the adjusted determination coefficient (R-Adj(2)) was 0.9812 and the level of significance was P < 0.0001. Optimum process parameters for a 6-log cycle reduction of Listeria monocytogenes were obtained: pressure, 448.0 MPa; temperature, 41 degrees C; and pressure holding time, 11 min. The adequacy of the model equation in predicting optimum response values was verified effectively by validation data.