[en] This review on radiolysis considers both the fundamental mechanisms and theory involved in radiolysis of pure water and systems containing major species existing in repository conditions. The amount of different molecules and radicals formed in radiolysis of water is a complex function of the type of radiation and dose rate, pH and ionic strength of water. The principal effects of the species present in water are to scavenge the radiolytic intermediates and products producing new species and changing the yield of radical and molecular products. Of the metals (Cu, Fe) and inorganic ions (Cl^-, HCO₃^-/CO₃^2-, NH₃/NO₂^-) considered, iron is the most important one and can participate in a number of reactions both with the primary and secondary radiolysis products and may effect both the H₂ and H₂O₂ yield. For the estimation of the overall effect of radiolysis in the repository both calculations and supporting experimental work is needed