Ab initio cluster calculations of electric-field-gradients at the Ta site in the ferroelectric LiTaO 3 crystal have been carried out for the temperature range 160 to 940 K. The calculations were made for the (TaO6)-7 cluster using the WT basis set for the tantalum and TZV basis set augmented with the polarization d -function (0.85) for the oxygen. The results of calculations of the V zz temperature dependence agreed well with experimental data.