The infrared absorption spectra of boron oxide glasses of low and high water content have been obtained in the 400- to 4000-cm.−1 region using thin films or fine powders dispersed in a liquid. A structural interpretation of the glass spectra has been made with the aid of the spectra of the closely related materials boric acid, orthorhombic metaboric acid, and partly deuterated boron oxide glass of high water content. It has been shown that the glass spectra are consistent with a random-network structure in which each boron is triangularly coordinated by three oxygens and that the presence of water leads to weak hydrogen bonding between oxygen atoms. No evidence for a substantial amount of tetrahedral coordination of boron by oxygen has been found in glasses of either low or high water content.