Abstract The luminescence properties of the Eu 3+ ion in the crystalline and glass modifications of Ln BGeO 5 -type compositions ( Ln = La, Gd, Y, and CaBPO 5 ) are investigated. The efficiency of the luminescence upon broad band excitation is higher in the crystals than it is in the glasses. Whereas crystalline GdBGeO 5 :Eu is a very efficient luminescent material, crystalline LaBGeO 5 :Eu and CaBPO 5 :Eu show only medium efficiency, and the glass modifications are of a low to very low efficiency. The influence of the charge and the size of the ion for which Eu 3+ is substituted is discussed. The influence of these cations on the efficiency of the luminescence of the Eu 3+ ion is well known for crystalline compositions, but is observed for the first time in the glass modifications, where they play the role of network modifiers. The undoped compositions show a blue luminescence. Further we observed Eu 2+ emission in the europium-doped CaBPO 5 glass. It shows inhomogeneous broadening, so that not only broad band but also a small amount of sharp line emission could be observed.