The electrochemical oxidation of tetrathiafulvalene monocarboxylic acid and its conjugate base in acetonitrile has been studied by electroanalytical (cyclic voltammetry, coulometry) and spectroscopic (UV, visible and electron spin resonance) methods. On the coulometric time scale (10-60 min) in perchlorate medium, anodic decarboxylation occurs to form the tetrathiafulvalene (TTF) dication. Non-stoichiometric radical ion salt intermediates are formed during the electrolyses and have been isolated. The salts are further oxidized by the TTF dication which results in an autocatylic ECE oxidation scheme for the overall process. Detailed oxidation mechanisms are postulated. © 1980 Elsevier Sequoia S.A.