MoO 3 TeO 2 glasses were investigated by Raman spectroscopy and differential thermal analysis, and transition temperature, thermal expansion and density were measured. Mo O bonds are present in the entire glass composition. The glasses contain TeO 4 trigonal bipyramids, TeO 3 + 1 polyhedra and MoO 6 octahedra as basic structural units. Glasses having low MoO 3 content contain MoO 6 octahedra having two Mo O bonds. As MoO 3 content increases, the fraction of Mo O bonds to Mo 6 + decreases. When MoO 3 content reaches 30-40 mol%; the structure of glasses shows close resemblance to that of MoTe 2 O 7 crystal. On the basis of local structural difference around second-component atoms between MoO 3 TeO 2 and WO 3 TeO 2 glasses, differences in the properties of both glasses are discussed.