Abstract : To assess the role of the monomer polarizability in the course of electropolymerization reactions, an ab initio study of the influence of an intense electric field (lo9 V m-') on the dipole moment and total atomic charges of HCN, CH,CN, CH,CHCN, CHgC (CN) 2 and CH,CHCCH has been developed at the STO-3G, 3-2 1 G and 6-3 lG* levels. The calculated polarizabilities of the three vinylic molecules are high, the induced dipole moment being 10% of the permanent one. The decrease of the atomic charge observed on the vinylic CH2 group is insuffkient for it to be solely responsible for the increase in its electrophilic character.