Peroxides in natural products have been recently received a considerable attention due to their various biological and pharmacological properties. Nearly 300 peroxides have been isolated and structually characterized from natural sources, mainly as constituents of Compositae and marine sponge, and occur randomly in about 10 other plant families. Among peroxides studied, sesquiterpene endoperoxide, quinghaosu, has been already clinically applied as a new antimalarial drug. Based on the peroxides reported, structural classification, natural distribution and biological and pharmacological activities are reviewed. Color reagent and spectroscopic identification of peroxide are also described.