Electrochemical doping and dedoping of vacuum deposited poly(p-phenylene) (PPP) films have been investigated by in situ spectrocyclic voltammetry (SCV). In a non-aqueous medium, a good correlation has been shown between the visible spectral change and the cyclic voltammogram. Reversible doping and dedoping were observed in the spectral change during the cyclic potential sweep. It was found from the SCV that two or more doping sites exist in the vacuum deposited PPP film. In an aqueous medium, spectral change took place with a delay after electrochemical potential sweep. It is suggested that diffusion of char ed ions into the PPP film was inhibited by hydration of the ions by water. The SEM images of the surface also suggested the inhibited mobility of the charged ions into the PPP film. The PPP film could be doped with both anion and cation reversibly. The new absorptions of the PPP film in a doped stale are probably due to the transitions from the valence band to the bipolaron state.