Lead-zirconate-titanate Pb(Zr,Ti)O-3 (PZT)-based actuators are being evaluated by the automotive industry for advanced fuel injection systems, including injection of hydrogen. However, hydrogen can penetrate PZT lattice with deleterious effects on the functionality and properties of PZT. The effect of long-term (200-1200 h) high-pressure (100 bar) hydrogen exposure on the microstructure and electrical properties of PZT has been investigated in the present work. It is found that while the hydrogen atmosphere has only superficial effects on the microstructure of bare PZT plates, it has considerable deleterious effects on the microstructure of electrode/PZT/electrode assembly. The degradation consisted of the development of a porous layer just beside the electrodes on the PZT surface, detachment of the electrodes from the PZT, and extensive damage to the Ag/Pd electrodes. The effect of hydrogen on the capacitance of the electrode/PZT/electrode assembly was also studied by online monitoring of the changes in capacitance in H-2; no noticeable changes were observed in capacitance during the hydrogen treatment under the given conditions.