In the present work, on the basis of a detailed experimental analysis, we propose a mathematical model for the interpretation of the hydrogenation of aromatic compounds during gasoil hydroprocessing. The model considers a lumped scheme for gasoil composition and assumes that hydrogenation/dehydrogenation reactions occur according to the Langmuir-Hinshel wood mechanisms, where hydrocarbons and hydrogen adsorption occur on different active sites. Kinetic rate constants were evaluated through the fitting of a set of experimental data obtained on a pilot unit processing with a commercial NiMo/Al2O3 catalyst a gasoil mixture in a wide range of operating conditions, spanning the typical industrial ranges of pressure, temperature and LHSV. Further, independent sets of data obtained with the same catalyst but different feed qualities are correctly predicted by the model, confirming its reliability. Also, the model is applicable for the interpretation of hydrogenation behavior with different types of commercial hydroprocessing catalysts. (C) 2004 Elsevier Ltd. All rights reserved.