The electrochemical behaviour of molybdenum trioxide formed on titanium was studied by cyclic voltammetry. Various redox reactions taking place at -240, -400 and -600 mV/MSE were analysed. The Mo(V) formed at -240 mV is reduced at -400 mV. The product formed at -400 mV subsequently undergoes a time-dependent chemical reaction leading to the formation of Mo(IV). Mo(IV) is also formed at -600 mV by means of an electron transfer reaction coupled with a chemical reaction. Cyclic voltammetric investigations of the formation and identification of Mo(IV) by chemical reactions coupled with electron transfer reactions are presented.