A series of Ag+-ion conducting composites consisting of glasses of the AgI–Ag2O–B2O3 system and hard Al2O3 powder matrix were synthesized by a high-pressure route (pressure 7.7GPa, temperature 100–200°C). The composition of the glasses was described by the general formula: xAgI·(100− x)(0.667Ag2O·0.333B2O3), where x =40, 50 and 60. Alumina powder (2μm average grain size) was added to the glass in 50/50 proportions (by volume). Conductivity, thermal behavior and microstructure of these composites are reported. Though the conductivity of the composites is lower than that of the constituent glasses, other properties like mechanical resistance to fracture are considerably improved.