Abstract: An improved method of presulfiding a hydrotreating or hydrocracking catalyst which minimizes sulfur stripping upon start-up of a hydrotreating or hydrocracking reactor utilizing such a catalyst. The method comprises the steps of contacting a hydrotreating or hydrocracking catalyst with elemental sulfur at a temperature below the melting point of sulfur, thereby forming a sulfur-catalyst mixture, and heating the sulfur-catalyst mixture to a temperature above the melting point of sulfur. Preferably, the sulfur-catalyst mixture is first mixed with at least one member selected from the group consisting of high boiling oils and hydrocarbon solvents to form a prewet mixture prior to heating at a temperature above the melting point of sulfur. Tail gas treating catalysts are also presulfided by these methods.