We have observed domain walls in ferroelectricLiTaO3crystals using a polarization and phase sensitive near-field scanning optical microscope. The strain induced birefringence was used to observe the domain walls. The domain walls are measured to be 1 &mgr;m wide and show a variation of strain along the domain walls probably due to defects. These measurements allow an estimate of the birefringence at the domain wall of6×10−5and associated shear strain of4×10−5.©1997 American Institute of Physics.