In order to perform an in-depth study on the electropolymerization mechanism of bis(alkyl)-substituted bithiophenes, poly[4,4'-bis(metylbutylthio)-2,2'-bithiophene] (poly-MBTBT) has been electrogenerated by using both potentiodynamic and potentiostatic techniques under different experimental conditions. Bidimensional spectroelectrochemical data have allowed us to obtain valuable information about both the polymer and the soluble oligomers electrogenerated in the process. The same kind of oligomers has been observed in the potentiodynamic and potentiostatic polymerization. (C) 2004 Elsevier Ltd. All rights reserved.