The intramolecular proton transfer process has been studied by measuring of the dipole moment, an average molecular weight, and UV/VIS spectra as a function of temperature and concentration in a few solvents of low polarity. Ten Schiff bases were selected for such studies, where steric repulsion of alkyl- and aryl-substituents in azomethine moiety enhances the strength of hydrogen bond and the proton transfer process. The self-association of species with intramolecular proton transfer has been investigated as a function of solvent polarity. Behaviour of these systems has been compared with those of Mannich bases, where intramolecular electron coupling between acid and base centres is considerably prevented by -CH 2 - bridge. A substantially different behaviour of these two types of compounds has been found out.