Glow-discharge electrolysis (GDE) has long been thought to proceedby a mechanism involving free radicals. Studies of the radical reactions have centred on the use of inorganic scavengers such as ferrous, cerous, ferrocyanide and azide ions. This thesis describes the application of the technique of spin trapping to GDE, and provides the first clear identification of the free radicals formed.Using 5,5-dimethylpyrroline-t-oxide (DMPO) as the spin trap, the radicals formed in the GDE of inert aqueous electrolytes were found to be the hydrogen atom and the hydroxyl radical. No evidence for the presence of the hydrated electron was found. In the GDE of aqueous solutions of organic substrates the main radical trapped was usually the result of hydrogen abstraction reactions.During the course of the spin trapping experiments, it was concluded that the spin adducts formed were extensively dimerised. This was most noticeable in the case of the hydrogen atom adduct where the concentration of monomer increased by 150% with a 200C rise in temperature.