This paper applies a statistical thermodynamic approach to the kinetics of microbial growth influenced by pH. A general equation is developed and shown to provide a good theoretical basis for the existing pH models that have been widely used to describe the effects of pH on microbial growth kinetics. Four experimental data sets are used to test the general equation developed. The four data sets exhibited a variety of functional curve shapes, for example, symmetrical and asymmetrical bell-shaped, when the specific growth rate of microorganisms is plotted as a function of pH. All four data sets are found to be well represented by the general equation. The existing pH model was, however, found to represent only one out of four data sets, i.e., the symmetrical case.