In this work we report the characterization and results of hydrothermal treatment tests performed on MCM-41 and Ti-MCM-41 materials at two temperatures, 450 and 550 degreesC. Based on BET analyses and XRD measurements, results showed a decrease in specific surface area, pore volume and pore size for both materials after the hydrothermal treatments. The Ti-MCM-41 material was more stable than the MCM-41. The specific surface area reduction for the hydrothermally treated Ti-MCM-41 samples at 450 and 550 degreesC was 16% and 29%, respectively. Similarly, there was a reduction of the inter-planar spacing of 30% and 33%, respectively, observed as a displacement of the main diffraction peak towards larger diffraction angles. We also report the conversion and selectivity of these materials in the HDS reaction of DBT. A higher conversion was obtained with the Ti-MCM-41 supported catalyst. (C) 2004 Elsevier B.V. All rights reserved.