Electrical depolarization has been observed in lanthanum-modified lead titanate ferroelectric thin films stressed by nanoindentation. A spherical metallic indenter was used as a top electrode to locally pole the films and then to measure the depolarization current intensity. The current intensity had distinctive maxima at given indentation forces. These are related to the stress thresholds for the depolarization mechanism, which is probably 90° domain wall movements. Knowledge of the depolarization stresses is necessary for the design of microelectromechanical systems that include a ferroelectric layer. © 2001 American Institute of Physics.