The invention pertains to a process for activating an hydrotreating catalyst comprising a Group VIB metal oxide and a Group VIII metal oxide which process comprises contacting the catalyst with an acid and an organic additive which has a boiling point in the range of 80-500° C. and a solubility in water of at least 5 grams per liter (20° C., atmospheric pressure), optionally followed by drying under such conditions that at least 50% of the additive is maintained in the catalyst. The hydrotreating catalyst may be a fresh hydrotreating catalyst or a used hydrotreating catalyst which has been regenerated.