Abstract: A process for catalyzing the sulfurization of olefins and the resulting products are disclosed in which the catalyst is a tertiary phosphine such as a trihydrocarbyl phosphine or a trihydrocarbyl phosphine sulfide. The catalyst is preferably soluble in the olefin and, in the presence of elemental sulfur, the reaction mixture is heated to a temperature sufficient to sulfurize the olefin. The catalyst enables the sulfurization to proceed at lower temperatures than would be employed without catalysis. Atmospheric pressure production is possible of high sulfur-containing olefins which normally boil or reflux strongly at or below sulfurization temperatures. In addition, the product of the catalyzed reaction has certain advantages, such as improved oil solubility with no subsequent dropout.