Oxynitride phosphate glasses have been obtained by ammonolysis of xLi(2)O (1-x)P2O5 (x=0.5, 0.55, 0.575) glasses and their electrical conductivity and lithium structural environment studied. Nitrided glasses were prepared through thermal treatment of the phosphate glasses under ammonia flow at temperatures below 800 degrees C. Nitrogen incorporation produces a sharp increase in conductivity for low nitrogen contents, while the activation energy decreases. Conductivity increase is very small or negligible for N/P ratios higher than 0.1, and the effect of nitrogen is analogous for all Li/P ratios. The increase in the electrical conductivity is explained through the structural modifications produced after the nitrogen substitution within the glass network. Li-6 NMR experiments show that the coordination number of Li+ decreases with N/P, which is interpreted as an increase in the Li-O bonds covalence. This effect of nitrogen on the lithium environment together with the increased glass density is thought to be counteracting the increase of conductivity for high nitrogen contents. (C) 2008 Elsevier B.V. All rights reserved.