The aging behaviour of conductivity in vapour phase deposited polypyrrole films has been investigated after storage in dry ambient temperature conditions. The decrease of conductivity with time is found to be complex suggesting a two-stage process. The rate of decrease of conductivity is also found to be dependent on the concentration of the dopant. Studies on changes in anisotropy and the X-ray photoelectron spectra suggest that morphological features and displacement of the dopant ions could be important factors governing the aging behaviour of these films. © 1997 Elsevier Science Limited.