This volume comprises six chapters on aspects of fundamental and applied electrochemical science that will be of interest both to researchers in the basic areas of the subject and to those involved in aspects of electrochemical technologies. Chapter 1 is the first part of a 2-part, major contribution by Joachim Maier on Solid State Electrochemistry: Thermodynamics and Kinetics of Charge Carriers in Solids. Part 2 will follow in volume 39 to be published in year 2005. This contribution reviews modern concepts of the equilibria involving charge carriers in solids in terms of concentrations of defects in solids and at grain-boundaries, including doping effects. Complementarily, kinetics of charge transfer and ion transfer are treated in some detail in relation to conductance, kinetics of surface processes and electrode-kinetics involving solid-state processes. This chapter will be of major interest to electrochemists and physicists in the semiconductor field and that involving ionic solids. In the second chapter, Appleby presents a detailed discussion and review in modern terms of a central aspect of electrochemistry: Electron Transfer Reactions With and Without Ion Transfer. Electron transfer is the most fundamental aspect of most processes at electrode interfaces and is also involved intimately with the homogeneous chemistry of redox reactions in solutions.