The resolution of the analytes was predicted from their known pK(a)* values and actual mobilities in nonaqueous methanolic solutions according to theory taking longitudinal diffusion as the only cause for peak dispersion. This leads to an equation of the resolution as a function of the pH*, as both selectivity and efficiency are dependent on the pH of the buffer. The experimentally obtained resolution values were in acceptable agreement with the predicted theoretical ones in most cases. This was demonstrated for substituted benzoic acids as analytes. The pK(a)* values needed for the calculation of the resolution were derived from the pH* dependence of the effective mobility. The pH* scale in methanol was based on conventional pK(a)* values of acetic acid and chloroacetic acid taken from the literature.