The theory of vibronic interactions is a new field of investigation in the physics and chemistry of molecules and crystals that goes beyond the separate descriptions of the motion of electrons and nuclei in the adiabatic approximation. A systematic treatment of the most important manifestations of nonadiabaticity (the Jahn-Teller, pseudo-Jahn-Teller and Renner effects) is given, including derivation of the vibronic Hamiltonian, proof of the Jahn-Teller theorem, determination of the adiabatic potentials of electronically degenerate and pseudodegenerate polyatomic systems, calculations of...