This paper reports the preparation of planar waveguides in an Er3+ doped tellurite glass with a composition, 15Ns2O-25WO3-60TeO2- 1Er2O3, by Ag+-Na+ ion-exchange. The glass was chemically stable during ion-exchange process. Single-mode and multi- mode planar and buried waveguides in the tellurite glasses have been prepared, which is the first demonstrated of waveguides in tellurite glasses fabricated by ion-exchange technique to the best of our knowledge. The depths of the waveguides could be controlled by varying ion-exchange temperatures and times. The diffusion parameters, diffusion coefficients and activation energy were estimated. It is indicated that the tellurite glass is a prospective candidate for active integrated optics.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.