Crystallization behavior of alpha-AgI was investigated by means of XRD, DSC, and FE-SEM from the melts and glasses of AgI-Ag2O-MxOy (MxOy = B2O3, GeO2, WO3). alpha-AgI microcrystals were formed by rapid quenching of melts with around 80 mol% AgI and also by heating of glasses with around 75 mol% AgI. In any system, alpha-AgI fine particles of about 20-40 nm in diameter were dispersed in the composites from the melts; there were no marked differences in microstructure among the samples in those systems. The alpha-AgI microcrystals included in the composites obtained from the melts had a large heterogeneous lattice strain at room temperature. The samples of those systems showed almost the same degree of lattice strain at room temperature. On the other hand, AgI-rich amorphous particles with 40-60 nm in diameter were dispersed in the twin-roller quenched glasses of any system with 75 mol% AgI, for which no X-ray crystalline peaks were observed. In those glasses being heated up to 95-120 degrees C, island regions of several hundreds of nanometers were observed; the island regions contained finely dispersed alpha-AgI particles of about 20-30 nm in diameter. It is noteworthy that the crystallization temperatures of alpha-AgI are much lower than the a-p phase transformation temperature (147 degrees C). The crystallization of a-AgI from the glass below the alpha-beta phase transformation temperature supports the possibility of the existence of alpha-AgI nuclei in the AgI rich amorphous particles in the as-quenched glasses with 75 mol% AgI.