In general, hydrogen peroxide is a stable and relatively mild oxidant and it can be regarded as the ultimate "green" reagent because water and oxygen are the only by-products. Besides the direct application of H₂O₂ in chemical processes more and more enzymatic syntheses based on hydrogen peroxide were developed. Different types of reactions can be addressed by using a hydrogen-peroxide driven biocatalysis (e.g. hydroxylations, epoxidations, sulfoxidations, halogenations, Baeyer-Villiger oxidations, decarboxylations). H₂O₂-driven reactions can often be used to substitute NAD(P)H dependent reactions. Therefore, laborious cofactor regeneration systems can be avoided by using H₂O₂-dependent enzymes. The tremendous increase in the number of publications dealing with this type of reactions clearly demonstrates the progress in this area in recent years. The described innovations range from new enzymes and types of reaction to novel reaction engineering approaches. This review aims to give the scope of possible advantageous applications of peroxyzymes and a critical discussion of their current limitations. The versatile reactions, the ecological advantageous and the great progress in the discovery and engineering of novel enzymes make a technical use feasible.