The intrauterine system (IUS) delivering levonorgestrel (LNG; Mirena), initially developed as a long-acting method of contraception, has demonstrated its efficacy and safety in a large number of users all over the world. The local delivery of a small dose of a highly effective progestin in the uterine cavity maintains the endometrium in a nonproliferative state and reduces the number of bleeding days, thus preventing anemia, an important medical benefit, especially in developing countries. In addition, the intrauterine delivery of a progestin allows the treatment of other medical conditions and prevention of endometrial hyperplasia, in postmenopausal women receiving estrogen therapy. During the perimenopausal years, the IUS provides an effective contraception as occasional ovulations occur. In addition, by its direct effect on the endometrium, it prevents the occurrence of menorrhagia, a frequent condition in the premenopause. After cessation of the ovarian function, when estrogen therapy may be initiated, the IUS would ensure endometrial protection as a transition to the menopause and as long as hormone therapy is needed. Although the circulating levels of LNG are very low, minor side effects related to the androgenic properties of LNG have been reported. In addition, the insertion of the system needs a skilled health provider and may be difficult or painful when the uterus is small or atrophic. The development of smaller devices is warranted for these specific situations.