In order to study the possibility for production of ultra low sulfur diesel in existent industrial plants, different tests of hydrotreating was developed in plant pilot. Hydrotreating of light gasoil (LGO) in two stages using a commercial catalyst of Co-Mo supported in alumina was made. The LGO was fed twice trough the reactor at operating conditions of industrial plants. The operal conditions for each stage were: pressure 56 bar, LHSV 1.65 h(-1), H-2/HC ratio 56 m(3)/Bl (hydrogen flow was once trough) and temperatures in the range of 613-653 K. Under the operation in two stages, the global LHSV of the plant decreases one-half. The performance of the hydrodesulfurization, hydrodearomatization, hydrodenitrogenation and olefins saturation reactions were studied. The obtained results show high removals of pollutants at different operating conditions. Final products with up to 10 ppm of sulfur were obtained. In terms of industrial operation, these results indicate that it is necessary to diminish the space velocity to values of 0.82 h(-1) with purification of make-up hydrogen to achieve the obtaining of ultra low sulfur diesel. (C) 2004 Elsevier B.V. All rights reserved.