Silver nanoparticles have been produced by -irradiation of silver solution in optically transparent inorganic mesoporous silica. The reduction of Ag+ within the matrix is brought about by hydrated electrons and hydroalkyl radicals generated during the radiolysis of the 2-propanol solution. The particles formed within the silica matrix were studied by electron microscopy, nitrogen sorption measurements, and absorption spectroscopy. The particles were mostly confined and dispersed in the pores of the mesoporous hosts. Absorption spectra show that the mean Ag clusters size increases with the irradiation dose. At high dose, agglomerated large particles are formed. In contrast, at a given dose, the effect of the dose rate has been clearly demonstrated to lower the cluster size. The silver particles within the silica matrix are stable in the presence of oxygen for at least several months.