The novel method with the use of resistance foil strain gauges is described and employed for the determination of the isothermal volume compressibility coefficient of xAgI-(1 -x)(Ag2O-P2O5) (0.05 less than or equal to x less than or equal to 0.5) glasses. It has been found that compressibility is dependent on pressure-time-history of the glass. The results are discussed and explained on a model assuming that high pressure causes the network to be more densely packed resulting in lower compressibility. Also, concentration of AgI in the glass affects the compressibility value. The linear dependence of compressibility vs. molar fraction of AgI has been found. The linear model of resultant compressibility of composite materials has been suggested to explain the observations.