A strain incompatibility arises between the electrically active and inactive parts of a partially electroded piezoelectric material. This leads to cracking perpendicular to the electrode edge. Symmetric partial electrodes of different widths were applied to lead zirconate titanate (PZT) plates to study the development of these cracks. Different cracking patterns appeared upon application of an electric field, depending on the degree of coverage and on the thickness of the plates. The apparent coercive fields are correlated to the degree of clamping and the amount of cracking in the specimens. Non-linear finite element modelling is used to analyse the material response.