Refractive index and molar refraction of Li2O-, Na2O-, CaO-, and BaO-Ga2O3-SiO2 glasses have been used to test the validity of a structural model of silicate glasses containing Ga2O3 glasses. Ga2O3 enters these types of glass in a similar manner as Al2O3. It is assumed that, for (SiO2/Ga2O3) > 1 and (Ga2O3/R2O) a parts per thousand currency sign1, Ga2O3 associates primarily with modifier oxides to form GaO4 units. The rest of modifier oxide forms silicate units with non-bridging oxygen ions. Silicate structural units have the same factors as found for binary alkali- and alkaline earth silicate glasses. Differences between experimental and model values suggest another structure for (Ga2O3/SiO2) a parts per thousand yen1.