Strongly adherent polypyrrole (PPy) films have been obtained by electropolymerization of pyrrole on pretreated iron and mild steel. Several chemical pretreatments of the metal surfaces have been compared. The results show that a treatment by 10% aqueous nitric acid inhibits iron dissolution without preventing the pyrrole oxidation. Very adherent thickness-controlled PPy films were obtained at constant-current in various aqueous media containing Na2SO4, K2C2O4 or KNO3. A maximum coulombic efficiency of 95% was obtained in the presence of KNO3 for a current density lower than 10mA/cm(2), but dropped to 70% and 50%, in the presence of Na2SO4 and K2C2O4, respectively, and for a current density between 2 and 4mA/cm(2).