B1 abstract the invention relates to a process for the sulphurization of catalysts for the hydrotreating of hydrocarbon feedstocks according to the invention a small amount of at least one orthophthalic acid ester is added to the sulphurization agent used to sulphurize the catalyst the catalysts thus sulphurized prove to be more active than conventionally sulphurized catalysts application_number US 55340900 A description the aim of the present invention is to make improvements to the sulphurization of the catalysts and to increase the activity of the catalysts in particular for the hydrotreating of hydrocarbon feedstocks it has now been found surprisingly that the joint use of a sulphurization agent and an ester of orthophthalic acid makes it possible to obtain catalysts which are more active with regard to hydrodesulphurization of hydrocarbon feedstocks than the catalysts sulphurized in the absence of this orthophthalic acid ester thus the present invention relates to a process for the sulphurization of catalysts based on metal oxide s comprising a stage of treatment of the catalyst with a sulphurization agent characterized in that an orthophthalic acid ester is added to the latter the present invention applies equally well to techniques for the sulphurization of the catalysts under u201c in situ u201d conditions and to those carried out.