Powders of pure silicon and gallium arsenide were reacted with molten silicate glass of a composition used in our prior work on CdS and CdTe quantum dots in glass [1–4]. After the Si or GaAs agglomerated particles had reacted with the melt for an hour, the material was solidified to obtain a gray-black glass. Ground powders of this glass were again mixed with additional base glass powders to dilute the concentration of the semiconductor, remelted, and cast into glass. Samples of silicon-in-glass showing green photoluminescence peaked at 530 nm were obtained. The GaAs-in-glass samples show absorption features in the optical spectra which suggest the possibility of quantum confinement.