We report optical waveguiding of a LiNbO3single−crystal film grown onto ac−plate LiTaO3substrate by liquid phase epitaxy from a new Li2O−V2O5flux. A film of about 3−&mgr;m thickness supported seven TE and two TM modes. Measurements of the mode indices indicated that the film is a ’’uniform’’ waveguide having constant refractive indicesno=2.2884andne=2.1914throughout the film. Attenuation was measured to be 5 and 11 dB/cm for TM and TE, respectively.