Differently stressed films of tungsten on silicon dioxide have been studied to determine the interfacial fracture toughness and the Mode I fracture energy release rate of tungsten on glass. Tungsten films with a low compressive stress (less than 1GPa) had nanoindentation tests performed on them to induce buckling. Using mechanics based models and the dimensions of the buckles the fracture energy release rate and the phase angle of loading (Ψ) were calculated to be between 3.8 and 13 J/m2. By varying the residual stress in the film it was possible to examine regions of pure shear (Mode II) interfacial fracture as well as mixed mode interfacial fracture toughness of this system. A similar tungsten film was then used as stressed overlayer on sputtered Pt films on silicon dioxide to determine the fracture energy release rate. Nanoindentation was required to induce buckling, as the overlayer alone did not cause spontaneous buckling. The stressed overlayer method and nanoindentation were used to determine the interfacial toughness of the Pt/silica system to be 1.4 J/m2.