Pulse radiolysis was used to study the mechanism of HO center dot-induced polymerization of poly(3,4-ethyl-enedioxythiophene), PEDOT, in aqueous solution. A step-by-step mechanism has been found which involves a recurrent oxidation process by HO center dot hydroxyl radicals produced by water radiolysis. Furthermore, the cation radical, EDOT center dot+, has been proposed as the promoter of the first step of polymerization. The determination of rate constants values and the attribution of transient and stable species were confirmed by molecular simulations and spectrokinetic analysis. Moreover, applying a series of electron pulses enabled in situ PEDOT polymerization. These polymers, which were characterized in solution or after,deposition, form globular self-assembled structures with interesting conducting properties. Such a synthesis initiated for the,first time by an electron accelerator gives us a glimpse of future promising industrial applications in the field of conducting polymers synthesis.