Five bioactive CaO - SiO2 sol-gel glasses (SiO2 = 50, 60, 70, 80 and 90 mol%) were characterised by N-2 adsorption and Hg porosimetry. The textural properties change according the composition of glasses. Surface area, pore volume and porosity increase whereas the average pore size decreases with the increasing of SiO2. No pores in the micropore region (diameter of pore, D-p < 2 nm) are detected. All the porosity is accessible to Hg indicating that samples do not contain closed pores. The gel glasses with 70 and 80 mol% SiO2 showed the highest pore volume in the macropore region (D-p>50 mn). Because these compositions present the highest rate of formation of the apatite layer under in vitro conditions, this property seems to be related with the increase of the pore volume in the macropore region. (C) 2004 Elsevier B.V. All rights reserved.