The insulator to conductor and conductor to insulator conversions of polyaniline have been studied by the in situ conductivity technique. Polyaniline was deposited by electropolymerization of aniline connecting two or more bands of gold electrodes. The gap between two gold stripes was 2 μm. Slow relaxation and hysteresis effects have been observed in different electrolyte solutions in the temperature interval from 5 to 45°C. The duration of the change of the resistance after a potential step is small (tens of seconds) in the potential region where the film is conducting, however, the relaxation may last for hours during conducting to insulating transitions. In the latter case, the behavior does not obey a simple logarithmic relaxation because at least two distinct slopes can be determined in the R versus ln t curves. The conductivity relaxation is in accordance with the previous results obtained by other techniques and can be explained by the existing theories.