The synthesis and properties of poly(3,4-ethylenedioxythiophene) (PEDOT) are reported. The polymer shows a low band-gap, 0.5 eV lower than that of polythiophene. This leads to very pronounced electrochromic properties since the doped polymer is almost transparent, with a sky-blue tint, and the neutral polymer is blue-black. The low band-pp also leads to the possibility of n-doping by electrochemical methods. The conductivity of the doped polymer is up to 200 S cm-1, and the stability is remarkable, much better than observed in our studies of the polythiophene and polypyrrole families.