Pilot scale hydrotreating experiments have been conducted on straight run high speed diesel oil (SR HSDO) using commercially available Co-Mo on Al2O3 catalyst. Kinetics of hydrodesulphurization and hydrodenitrogenation are studied using the models that took into account the physical and chemical complexities of the three phase system. Correlations are developed to predict the product properties based on operating conditions. The results show a good agreement with the experimental data.