We report the simultaneous in situ electrochemical, optical, and surface morphological studies of conjugated polymer ultrathin film formation using a novel combined electrochemical instrumentation-surface plasmon resonance spectroscopy-atomic force microscopy. The initial stages of the electropolymerization of poly(3,4-ethylenedioxythiophene) films on flat gold electrode/substrates were observed in all three experiments simultaneously. In addition to the electrochemical information obtained, the surface plasmon optical technique showed the deposition of the film, and provided electrochromic behavior of the deposited film. Simultaneously, atomic force microscopy gave surface morphological properties and domain growth of the film. The complementarity of the information obtained from the combined techniques is useful for the investigation of polymer growth mechanism between cyclic voltammetry and potentiostatic deposition methods. (c) 2006 American Institute of Physics.