The fatigue behavior of lead zirconate titanate ceramics (PZT) has been studied under electrical and mechanical drives. Piezoelectric fatigue was studied using a mechanical method. Under ac mechanical drive, hard and soft PZTs showed an increase in the longitudinal piezoelectric constant at short times, reaching a maximum at intermediate times. Systematic investigations were performed to characterize the electrical fatigue behavior. A decrease in the magnitude of the remanent polarization was observed, which was relatively high for soft PZT. The dynamics of fatigue have been shown to scale to a hierarchical relaxation process, and this is typical of random field systems. (C) 2002 American Institute of Physics.