A significant fraction of the sulfur species in diesel fuel can be removed in a conventional hydrotreater. To meet future more stringent sulfur specifications, this conventionally hydrotreated liquid product may be fed to a second hydrotreater to remove residual refractory sulfur species. The hydrodesulfurization reactivity of such prehydrotreated distillates is driven primarily by the feed nitrogen content in a linear fashion. The genesis of this observation is discussed. (C) 2004 Elsevier B.V. All rights reserved.