Hydrodesulfurization (HDS) and hydrodemetallization (HDM) of Maya crude were carried out in a high pressure (5.4 MPa) micro-reactor close to industrial practice. The effect of support preparation (gamma-alumina) was compared using different preparation techniques. The different support preparation methods leading to a variation in textural properties of the supports and its characterization provides important information about their applicability for Maya crude processing. Ammonium carbonate prepared supports provide improved pore size distribution as well as high pore volume. The prepared catalysts are effective for HDS and HDM, having less formation of deteriorating substances such as Ni and V with more stable behavior against time-on-stream. The HDM activity increases while the HDS activity decreases with increasing average pore diameter. Laboratory prepared catalysts showed comparable performance as well as stability in comparison with commercial catalysts against hydrotreating of heavy Maya crude feed. Among all prepared catalysts, better porosity containing catalysts represent higher and stable activity for HDM as a function of time-on-stream. The comparison of catalyst activity was carried out with commercial one which contains TiO2 and higher amount of molybdenum. The results of activity and stability of catalyst protrude distinct contribution of pore size distribution of support which has more capabilities to retain metal deposition as well as better diffusion of complex organo-chelating metals (V, Ni, etc.). (C) 2004 Elsevier B.V. All rights reserved.