The action of estrogen in the female reproductive organs is well known in terms of the expression pattern and gene regulation of the estrogen receptor (ER). The significance of ERs in female reproduction is undisputed. The role of the androgen receptor (AR) is less clear. Clinical hyperandrogenism, a typical feature of polycystic ovary syndrome (PCOS), highlights pathological androgen production by the ovary. By contrast, the physiological impact of androgen action in female reproductive organs remains elusive. Androgens affect folliculogenesis in a variety of experimental approaches and ARs are expressed in developing follicles. Recent observations have discovered that inactivation of ARs in female mice results in premature ovarian failure (POF), indicating that normal folliculogenesis requires AR-mediated androgen action. Moreover, these results imply that POF might be caused by impairment of AR-mediated androgen action.