Preparative, optical, electrochemical and spectro electrochemical studies of polypyrrole and polythiophenes in a bilayer configuration, conducted by the present author, are reviewed. A new electrochemical process has been found that leads to the bilayer configuration with the conducting polymers as the outer layers. These studies have presented the first examples that the conducting polymers are mediatively electrolyzed. Electrochemically driven Phase Separation (ECPS) of electropoly merized polymer components is proposed as the primary process in the course of achieving the bilayer configuration. We have shown that the progress of the electrochemical process is described as a systematic decrease of β (complementary charge transfer coefficient). Taking advantage of the specific mode of charge injections of the bilayer configuration, transiently occurring polarons have been detected in poly(3-methyl-thiophene) for the first time.