Undoped and Sb-doped SnO2 sol-gel derived thin films have been prepared for the first time from tin (IV) ethoxide precursor and SbCl3 in order to be utilised for gas sensing applications where porous silicon is used as a substrate. Transparent, crack-free and adherent lavers were obtained on different types of substrates (Si, SiO2/Si). The evolution of the Sn-O chemical bonds in the SnO2 during film consolidation treatments was monitored by infrared spectroscopy. By energy dispersive X-ray spectroscopy performed on the cross section of the porosified silicon coupled with transmission electron microscopy, the penetration of the SnO2 sol-gel derived films in the nanometric pores of the porous silicon has been experimentally proved. (C) 1997 Elsevier Science S.A.