Surviving Salmonella Typhimurium (S. Typhimurium) cells in mayonnaise were monitored during storage at 10 to $40^{circ}C$ at pH of 3.7 and 4.0. The survival of S. Typhimurium in mayonnaise was influenced by pH and storage temperature. The fastest decline in the viability of S. Typhimurium was observed at $40^{circ}C$ and the slowest decline was observed at $10^{circ}C$. Death rates were faster at pH 3.7 than at pH 4.0 at the same temperature, except for 30 and $40^{circ}C$. With all experimental variables, linear regression analysis showed a good fit ($r^2=0.8564$ to 0.9904). This model is appropriate for predicting death rates on the basis of a coefficient of determination of $r^2=0.87$, a mean square error of 0.00055, a bias factor of 1.0112, and an accuracy factor of 1.30958. Our model provides a reliable prediction of the death rate of S. Typhimurium in mayonnaise based upon the combined effects of temperature and pH.