Al2O3 and TiO2 were sintered with three types (lead, zinc, bismuth) of borosilicate glass. Their microwave dielectric properties and sintering behavior were investigated as functions of glass type, glass addition (10~50 vol%) and sintering temperature (600~950°C for 2 hrs). Sintering characteristics were well described in terms of softening temperature, second phase, and excessive liquid. In particular, Bi2O3 addition to the glass enhanced reaction with Al2O3 and TiO2 to form liquid phase and second phase. In terms of dielectric properties glass/Al2O3 composites for application to substrates while glass/TiO2 composites for filters were shown to be appropriate.