4-Substituted (perfluoroalkylsulfonyl)benzenes have been synthesized by the oxidation of 4-substituted (perfluoroalkylthio)benzenes with hydrogen peroxide, anhydrous chromic oxide and potassiumpermanganate in good yields. 4-(Perfluoroalkylsulfonyl) anilines have been also prepared by the reduction of the corresponding nitrobenzenes.