Sulfides are oxidized to sulfoxides by stoichiometric amounts of perfluoro-cis-2, 3- dialkyloxaziridines 2. The reactions proceed at-40 OC with nearly complete selectivity and very good yields. Sulfoxides are also oxidized easily by 2 under mild conditions to corresponding sulfones. The oxidation of some bioactive sulfides (promazine, albendazole, biotin, and others) is also reported.