This work contains selected papers from the June 2003 XI International Conference on Chemistry of Organic and Organoelemental Peroxides, held in Moscow, as well as articles on theoretical chemistry, synthesis of valuable oxygen-containing compounds, and the technology and chemistry of polymers. Some specific topics include peroxide oxidation of arabinogalactan, hydrogen peroxide decomposition in the presence of manganese and copper porphyrins, and specifics of thermal and photo decomposition of peroxyalkynes in solution, as well as estimating the explosion hazard of organic peroxides, the role of nitroso oxides in photochemistry, chemical reaction by low power microwave irradiation, and the kinetics of lipid oxidation and lipid hydroperoxide decomposition in the presence of amphiphilic compounds.