The paper reviews a recent research on the role of glutathione (GSH) in the male and female germ cells as well as during the early stages of embryo development in mammals. In both the male and female gametes, GSH is involved in the protection of these cells against oxidative damage. Glutathione has been implicated in maintaining the meiotic spindle morphology of the oocyte. After fertilization, this thiol plays an active role in the formation of the male pronucleus, and has a beneficial effect on early embryogenesis to the blastocyst stage. GSH concentrations change within the oocytes during meiotic maturation and its synthesis is regulated by gonadotropins. Furthermore, GSH concentrations in the maturing spermatozoa gradually decline during spermatogenesis. This review also addresses the important role of cumulus cells in glutathione synthesis.