This monograph is the first in world chemical literature that has the review, generalization and systematization of all the problems of physical chemistry of organic peroxides. The general information concerning organic peroxide classifications, the methods of their synthesis is given. The properties of peroxide bond are briefly considered. The structure of organic peroxides is analyzed in detail. The features of NMR spectroscopy as well as vibration spectroscopy of peroxides of a various structure are considered. Experimental data on thermal decomposition of organic peroxides in the gas phase and in solution are generalized. The influence of high pressure and cage effect on thermal decomposition of peroxides is described. Further, the acid-catalyzed reaction of decomposition, synthesis and transformations of organic peroxides are considered. The theoretical approaches to determination of thermodynamic properties of organic peroxides are considered. In the appendix kinetic and thermodynamic parameters of the representative set of peroxides are described and the areas of their application are specified. The examples of synthesis of the large set of organic peroxides are given.