Raman spectroscopy has been used to measure the fraction of tetrahedral silicate units connected at three corners into the network (Q(3)) in binary lithium silicate glasses and also in the more complex borosilicate glasses used for waste immobilization. Agreement within experimental error was obtained with Si-29 MAS NMR measurements of the same samples. Raman provides an alternative method of structural determination for silicon-containing glasses with a high content of paramagnetic species where NMR loses resolution. Analysis was performed on borosilicate glasses containing up to 11.98 mol% Fe2O3 and the Q(3) values obtained by Raman spectroscopy agree within error with the published Si-29 NMR results from borosilicate glasses containing the equivalent quantity of Al2O3. (C) 2007 Elsevier B.V. All rights reserved.