The electrochemical polymerization of bithiophene was performed in water in the presence of either sodium dodecyl sulfate (SDS) or hydroxypropyl-beta -cyclodextrin (HP beta CD), mainly under potentiostatic conditions. The polymerization process was followed by electrochemical quartz crystal microbalance in order to determine the yield as a function of the current and the potential. Comparable results are obtained in both media (SDS and HP beta CD). The polymerization process appears to be critically dependent on the potential and seems to be rate-limited by slow bithiophene diffusion through an interface consisting of accumulated CD or SDS on the electrode surface.