Alumina and lanthana glasses in ternary systems containing BaO and SiO2 are useful for the vacuum deposition of thin film lightguides.1 Evaporated with an electron gun they produce low-loss films of refractive index 1.64-1.66. These can serve as the interconnecting lightguide for components of an integrated optics system. Understanding the refraction process at the boundaries of refracting components is vital. This paper describes experimental studies of refraction at a straightline boundary between evaporated glass lightguides and evaporated thin film overlays of Sb203 with index 2.10. In the guide the angle of incidence on the boundary was 60°. Refraction was measured versus overlay thickness. As an example, for lowest order modes, a lightguide optically 2.4 quarterwaves thick with a 1.8 quarterwave overlay refracts a HeNe beam 7° in TM polarization and 11° in TE. The overlay edge was tapered a width of 1 mm. The refraction process is a continuous direction change through the taper. Snell's law gives the total change if mode indices on each side of the boundary are used. The work was supported by the Air Force Office of Scientific Research (AFSC), The United States Air Force, and the Army Research Office, United States Army.