The local environment around Er 3‡ ions in wet and densi®ed (at 900°C) silica xerogels (pure and co-doped with aluminium) has been studied at the Er L 3 -edge by X-ray absorption spectroscopy using the ¯uorescence detection technique. The radial distribution functions (RDF), reconstructed from X-ray absorption ®ne structure (EXAFS), show several changes in the local co-ordination of erbium ions upon densi®cation: shortening of the Er±O and Er±Si/Al distances, decrease of the co-ordination numbers and broadening of the Er±O RDF. The e€ect of Al co-doping is clearly discerned by EXAFS in both the ®rst and second co-ordination shells for densi®ed gels and mainly in the second shell for wet gels. For increasing Al content, the interatomic distances between erbium ions and the second co-ordi-nation shell ions become longer and have narrower distribution. A preferential bonding of Er to Al ions is clearly detected, with increasing ordering at higher Al content. EXAFS does not show evidence of a clustering for Er 3‡ ions after densi®cation: the short range Er±Er co-ordination is absent or not detectable in the present experiments. Ó 2001 Elsevier Science B.V. All rights reserved.