Raman spectra of LiTaO3 single crystals with various stoichiometries were measured to investigate the compositional uniformity of these crystals. Raman spectra mapping demonstrates a spatial variation of the widths of the phonon bands for stoichiometric, congruent, and quasi-congruent samples. A significant radial compositional inhomogeneity is found to be a common feature of commercially available wafers having a near-congruent crystal composition (i.e., x c ={[Li2O]/([Li2O] +[Ta2O5])}×100%=47.85-48.50%) grown by the single-crucible Czochralski method. A maximum value of the composition gradient x c for a radial inhomogeneity of 0.163 and 0.036%/cm is measured for thin wafers diced from so-called congruent (vendors' value of Δx c =48.50%) and quasi-congruent (x c =47.88%) crystals, respectively. In crystals grown from highly Li-rich melts (starting composition 54.5 mol% Li2O), a drastic spatial dependence of Raman bandwidths, indicating a significant gradual compositional inhomogeneity throughout the crystal, is found, which is due to a change of the melt composition during crystal growth. In contrast, the Raman bandwidths of near-stoichiometric crystals fabricated by a vapor transport equilibrium (VTE) technique are found to be constant, i.e. these crystals are practically compositionally uniform. This conclusion has been confirmed by mapping the photoluminescence intensity, evidencing Δ x c≤0.006%/cm in near-stoichiometric VTE-treated crystals. © 2009 Springer-Verlag.