A study has been made of the amidation of m-toluic acid by diethylamine in the presence of different heterogeneous catalysts. Thermodynamic characteristics and kinetic parameters of the reaction have been determined. The dependence of the activity of catalytic systems on the pK(a) of the acids with which they are modified has been established. On the basis of an analysis of the data obtained, a new catalyst calcium hydroxylapatite - has been proposed for such processes.