It has been known for many years that administration of estrogen, a so-called female hormone, has harmful effects on male fertility. However, studies employing transgenic mice deficient in estrogen receptors reveal substantial roles for estrogen in male fertility. The aim of this article is to review and summarize the current knowledge on the estrogen receptor localization in male reproductive organs including male germ cells of rodents. Also, informations about the mice models with disrupted estrogen signaling and associated phenotypes will be provided.