Early menopause due to an exhaustion of the ovarian follicles before the age of 40 years occurs in approximately 1% of women in this age range. Clinical signs of estrogen deficiency with amenorrhea and sterility are usually confirmed by hypergonadotrope hypogonadism at laboratory tests. The syndrome is to be differentiated from gonadotrophine resistant ovaries and rare gonadotrope adenomas. Ovary biopsy shows more or less complete destruction of the follicles. There are many causes of early menopause including abnormal number or structure of chromosome X in 15-20% of the cases. Certain metabolic disorders and viral infections can also be incriminated. Finally surgery, radiotherapy or chemotherapy can be the cause of iatrogenic menopause. To determine prognosis, the woman's follicular capacity must be estimated. Estrogen therapy is currently the best choice to preserve chances for ovulation and pregnancy. When there is no remaining follicular capacity, ovum donation may be a solution. Finally, all patients should be given hormone substitution therapy due to the long-term risk of estrogen-progesterone deficiency.