PR Spring bitumen was hydrotreated in a fixed-bed reactor over a commercial Mo/alumina hydrodemetallation (HDM) catalyst. Hydrodenitrogenation (HDN), hydrodesulfurization (HDS), hydrodemetallation. Conradson carbon residue (CCR) reduction, and residuum conversion were studied as a function of process operating conditions (T = 675-685 K, WHSV = 0.26-1.55 h(-1) and reactor pressure = 11.1-16.6 MPa). The hydrogen-to-oil ratio was fixed at 890 m(3)/m(3) (5000 scf H-2/bbl). The degree of sulfur removal was greater than residuum conversion and nitrogen removal with increasing temperature and contact time over the commercial HDM catalyst. Nitrogen conversion was lower than the conversions of the other species in all cases. Reactor pressure did not exert a significant influence on nitrogen and sulfur removal and CCR and residuum conversion.