Every woman has already as an embryo an “ovarian reserve”, i.e. a set amount of primordial follicles, which cannot grow any further. Even before birth, a part of the ovarian reserve is lost. This reservoir is continuously reduced with age. Especially after the 35th year, follicular atresia becomes accelerated. In this review, methods for determination of the ovarian reserve are presented and evaluated. The most important parameters are the value of AMH and the number of antral follicles. Of secondary importance are the measurement of FSH and oestradiol at the beginning of the follicular phase and inhibin B determination. In addition, the damage to the gonadal function by different factors and possibilities of fertility preservation are presented. Such possibilities are the transposition of the gonads before radiotherapy, the use of GnRH analogues and the cryopreservation of embryos, oocytes and ovarian tissue.