Simultaneous gp.c. and cyclic voltammetry measurements were carried out in the course of the electrocatalysed polymerization of various 3,6-dibromo(N-alkylcarbazole)s. The evolution of the molar mass population distribution as a function of the electrolysis time reveals a step polymerization process, while showing a termination of the chain growth due to the occurrence of monobrominated species. The consumption of the catalytic species corresponds in a first step to an increase in the chain length, while after given periods there is no more chain growth related to the continuous consumption of the catalytic precursor. The study of the effect of the initial [monomer]/[catalyst] ratio on the molar mass population evolution indicates that the coupling of Ni(0)-activated species is responsible for the chain growth.