Abstract: Phosphorylsulfenyl halides are added to monoolefins, multiolefins, conjugated multiolefins and acetylenic compounds. 1,2-Markownikov oriented adducts are the principle products when conjugated diolefins are employed as the starting feedstock. Anti-Markownikov adducts are obtained as major products when unsymmetrical monoolefins and nonconjugated multiolefins are used as the starting material. The addition reactions are conducted at low temperatures. The materials which are obtained are of interest as pesticides and as intermediates in the synthesis of pesticides.