Electrochemistry in the absence of a contacting electrolyte solution, using ionically conductive polymers of perflurosulfonic acid (Nafion) coatings and membranes, is reviewed. Various types of reference electrodes, including a polymer Ag/AgCl electrode and Ag directly sputtered on the Nafion membrane, were used. Voltammetry of model redox couples, such as potassium ferricyanide and various ferrocenes, was conducted in a solid-state configuration and compared to that obtained in aqueous solution. Dioxygen reduction catalyzed by an electropolymerized metalloporphyrin with a Nafion film serving as polyelectrolyte, shows similar features as observed using the modified electrode concept. However, catalysis of O₂ reduction in the presence of the cobalt (II) ammoniacal complex is more effective in the solid-state configuration. Dioxygen reduction in this case occurs 800 mV more positive than obtained in aqueous solution. New applications of solid-state electrochemistry in the fields of electrodeposition, monitoring of acidic gases and electrocatalysis are also reported.