The perovskite phase BaTiO3have been electron irradiated at varying temperatures and beam directions. The dislocation loops produced after room temperature irradiation of BaTiO3have been analyzed and found to lie on the (110) ferroelectric domain boundaries. These loops were of the typeb=l/2[011] (100) andb=l/2[101] (010) and were interstitial in nature. The loops nucleate as square faulted loops which unfault in to round loops. The stacking fault energy was calculated as ∼90 mJm−2. No defect clusters were observed to form at high temperature, though disordering on the atomic scale was believed to occur as, on cooling, ferroelectric domains are disrupted.