The life of Tafel equation is considered briefly as evolution in the understanding of Tafel's empiric parameters in the framework of various phenomenological and theoretical approaches. Modem theories of the interfacial charge transfer reactions are employed to explain the behavior of transfer coefficient versus electrode overvoltage and deviations of this quantity from 0.5 at low overvoltage. The effects of intramolecular reorganization, orbital overlap, reactant quantum modes and solvent dynamics are addressed and illustrated by model calculations. An attempt is made to propose new explanations of some data reported in the literature. (c) 2006 Elsevier Ltd. All rights reserved.