Laser‐induced optical index damage in LiNbO3and other pyroelectrics of ABO3structure is discussed in the light of recent results of stoichiometry investigations. The damage is attributed to the presence ofB‐excess stacking‐fault defects. The dc photovoltaic effect in LiNbO3as well as the detailed spatial distribution of refractive‐index variation is explained in terms of photoinduced variation of the macroscopic spontaneous polarization density. This variation results in a polarization charge‐density distribution, and an approximately compensatory space‐charge distribution. The index damage results from the polarization‐based electrooptic effect.