Sex-steroid-related tumours in women are represented by breast cancer and endometrial cancer, but a possible relationship may exist between sex steroids and both ovarian and colon cancer. Unopposed oestrogen therapy is known to increase the risk of endometrial cancer and is appropriate only for hysterectomized women. In women with an intact uterus, an appropriate combination of oestrogen and progestin does not appear to increase-and may even decrease-the risk of endometrial cancer. Current users of HRT seem to benefit from a reduced risk for colon cancer. As for epithelial ovarian cancer, the present data are very conflicting. The association between replacement hormones and this malignancy seems to be stronger for unopposed oestrogen than for oestrogen-progestin treatment. Data available at the moment do not allow discriminating for dose, routes of administration, bioavailability and tissue effects of different compounds so that it is inappropriate to consider all forms of HRT jointly. The future of HRT in post-menopausal women lies in the individualization of the therapy based upon personal risk factors and characteristics.