Bis(trimethylsilyl)peroxide, Me3SiOOSiMe3, ( ) BSPO oxidizes phosphines and phosphites to respective oxyphosphoryl derivatives with retention of the configuration at the phosphorus atom. It also converts thiophosphoryl function to oxyphosphoryl function with inversion of the configuration at phosphorus. High yields and high stereoselectivities of these processes render them useful for the synthetic application. Considerable attention has been recently paid to the oxygenation of organophosphorus compounds as a method of the generation of oxyphosphoryl function, particularly in connection with fast development of the chemistry of bioactive phosphorus containing products. During multistep synthesis of these products chemists often encounter the problem how to perform the oxygenation at the phosphorus centre in chemo-regio-and/or stereoselective way to obtain the intended product with a high yield and a high degree of purity [l-41. Although a variety of oxygenation methods exists many of them suffer from deficiencies giving byproducts and showing a poor selectivity. We present in this paper synthetic results indicating that BSPO meets requirements of versatile oxygenation reagent for the selective generation of oxyphosphoryl group. It is able both, to transfer oxygen to trivalent phosphorus as well as to convert the thiono phosphoryl compounds into the corresponding 0x0 derivatives, in a highly selective way. Bissilyl peroxides are relatively easily accessible [5-71 and they were shown to oxidize readily triorgano phosphines and triorgano phosphites [81. In contrast to the reaction of organic peroxides the mechanism of oxygenation with BSPO is ionic rather than free radical [9] what makes it even more promising as agent for selective oxygenations. It may be easily purified by distillation and it is soluble in many organic nonhydroxylic solvents. During oxygenation, BSPO is reduced to hexaorganodisiloxane, which being chemically inert, does not react with the phosphorus product. A good example of the utility of BSPO in the P(II1) -P(IV) oxidation is the conversion of (dimethylphenoxysilylalkyl)diphenyl phosphines to the corresponding phosphine oxides. BSPO