An increasing incidence of endometrial cancer caused by a higher life expectancy and a number of other facters (i.e. obesity, diabetes, hypertension, lower pregnancy rate) as well as the unfavorable location for early detection when compared with cervical cancer has initiated this review in order to single out women with increased risk. Clinical characteristics of patients with endometrial cancer represented by age, menstrual disorders, reduced fertility, obesity, diabetes, hypertension, hirsutism, hyperplasia of the ovarian stroma or hilus cells in connection with an increased oestrogen effect in the vaginal smear and proliferative changes of the endometrium can be explained by extraglandular respectively peripheral aromatization of androgens to oestrogens, particular by the conversion of androstenedione to oestrone. This is supported by an increased plasma oestrone/oestradiol-ratio and increased conversion rate with age and overweight. In vivo- and in vitro-investigations have demonstrated the participation of adipose tissue in peripheral oestrogene production. The compiled data point towards the importance of the extraglandular oestrone production for the etiology of endometrial cancer by effecting the endometrium over a long period of time. The counter action of the normally cyclic changes of oestradiol and progesterone is lacking. Therefore, a dysoestrogenic effect of oestrone upon the endometrium can be fully effective, depending on the hormone receptor content of the respective endometrium. Based upon these data including recent publications, pre- and postmenopausal oestrogen therapy has to be critically reevaluated.