Hydrodenitrogenation (HDN) of pyridine, one of the organo-nitrogen compounds found in petroleum and synfuels, is studied over presulphided and unsulphided Mo-zeolite catalyst in an integral fixed bed reactor between 525-573 K, W/F of 42-210 h g-cat/g-mol pyridine at 69 atm pressure and a H-2/Pyridine ratio of 13. Experimental results show that at 623 K the conversion of pyridine over the presulphided catalyst was 1.5 times of that over the unsulphided one, whereas the increase in selectivity was about 5 folds. This catalyst gives similar activity to that obtained with commercial Ni-Mo supported on alumina catalyst, but lower conversion. The HDN of pyridine occurred through the formation of piperidine, alkylpiperidines, and finally hydrocarbons. A Langmuir-Hinshelwood type rate expression satisfactorily represented the data. The apparent overall activation energy of the reaction (over sulphided catalyst) is found to be 15.6 kcal/g-mol.