Two glutathione peroxidase genes (gpx5 and gpx3) were found to be expressed in the mouse epididymis. Gpx5 was shown to be epididymis specific and restricted to the caput epididymidis, while gpx3 was found to be expressed in a wide array of tissues including the caput, corpus and cauda epididymides. Both single copy genes are regulated by androgens as well as being developmentally regulated during postnatal ontogenesis of the epididymis. In this report data collected to date concerning the mechanisms by which these genes are regulated in the mouse epididymis are summarized. The putative roles of these antioxidant enzymes in the sperm maturation process are discussed.