In situ resonance Raman (RR) and reflectance spectra of different charged species produced in the electrochemical oxidation diphenylammine (DPA) in 0.1 M tetraethylammonium tetrafluor⊙borate (Et4NBF4)+ acetonitrile solution at the platinum electrode have been investigated. The in situ RR and reflectance spectra have been also investigated during the reduction of these species. The diphenylbenzidine (DPB), diphenylbenzidine radical cation (DPB+.) and dication (DPB2+) species have been characterized as the main products of DPA oxidation. The in situ reflectance spectra of a platinum electrode in the presence of DPB as well as the effect of the addition of acid on the oxidation process have been investigated. The results have shown that the disproportionation reaction 2DPB+.+H+ ⇄ DPB2++DPBH+ plays an important role in the oxidation process of DPA and that it does not occur in the oxidation of DPB. During the reduction of the oxidation products it has been observed that the RR signals and the absorption band of the DPB2+ disappear faster than those of the DPB+. indicating that the synproportionation reaction DPB+DPB2+. α 2 DPB+ occurs.