Electrochemical properties of electrogenerated poly[4,4'-bis(butylsulphanyl)-2.3'-bithiophene] have been studied. with particular attention to the charge-discharge processes. The possibility of both p- and n-doping is indicated. Doping and relevant de-doping processes of the specific polymer have also been considered in the context of the more general, still un-solved problem of the analysis of the mechanisms that al-e operative in the case of simple polythiophenes. In situ spectroelectrochemical measurements have been used to support the electrochemical results and both in situ UV-visible NIR spectroscopy on neutral, p- and n-doped forms of the polymer, and ex situ IR measurements have been performed. (C) 2001 Elsevier Science Ltd. All rights reserved.