Organoselenium compounds find applications in organic synthesis, materials synthesis, ligand chemistry and biologically relevant processes. This review deals with the use of various synthetic organoselenium compounds as mimics of glutathione peroxidase (GPx), a selenoenzyme which catalyses the reduction of a variety of hydroperoxides and protects the cell membranes from oxidative damage. The mechanism by which these compounds catalyse the reduction of peroxides is also reviewed. The cyclic selenenamides and diselenides with suitably positioned substituents exert their catalytic activity by a mechanism similar to that of the natural enzyme.