The transition of polypyrrole (PPy) film from the electroactive to the electroinactive state during the immersion process in alkaline solution was investigated by the use of voltammetry and in situ FTIR spectroscopy. The mechanism of this process was proposed to involve the attack of hydroxide ion on the PPy molecule and its rate constant was measured. The electroinactive PPy film gives rise to a linear relationship between log(I/V) and V-1/2, which indicates it might be suitable for use in microelectronic devices.