Phosphorus oxynitride glasses containing up to 17 wt% N and up to 2.5 wt% H were prepared by decomposing NH4H2PO4 in ammonia at 720°C for various times. In general, glasses with greater N-contents have higher dilatometric softening temperatures, lower thermal expansion coefficients and better aqueous durabilities. X-ray photoelectron spectroscopic analyses reveal that N is chemically incorporated in both PNP and PNHx bonds. The hydrogen species, including -OH groups, depolymerize the glass structure, counteracting the effects of the cross-linking phosphorus-nitride bonds on the glass properties. © 1990.