A no. of (Eu,Y)-doped Si-Al-O-N glasses were prepd. and their optical properties examd. Eu was found to be present in the divalent instead of the trivalent state due to a reaction between the Eu3+ and the chem. incorporated N3- during the prepn. of the glasses. The luminescence characteristics were found to be negligibly influenced by the O/N and Si/Al ratio, but appear to be strongly dependent on the concn. and type of modifying cations (Eu,Y). As a function of the cationic compn. the emission shifts from wavelengths below 500 nm to wavelengths as long as 640 nm, which is very unusual for Eu2+ contg. compds. This shift to longer wavelengths is ascribed to a combination of energy transfer between the different sites and change of the Eu2+ site distribution.