The use of hormone-releasing intrauterine devices has been on the increase for the last three decades. To date, evidence of their long-term efficiency is available. The aim of the present paper was to briefly review beneficial prophylactic effects of the levonorgestrel-releasing intrauterine system on the incidence of a variety of malignancies in women. Such an influence is of a particular importance in the light of the currently observed increased prevalence of endometrial and cervical adenocarcinomas. Low-dose releasing intrauterine systems are also available, but the hard evidence-based medical data have been derived primarily for Mirena® (Bayer) device, which topically releases from 20 to 14 μg of levonorgestrel daily. Consequently, the risk of developing endometrial carcinoma in Mirena® users is lowered by as much as 50% compared with the general population risk. To a lesser extent, the intrauterine system decreases the risk for cervical adenocarcinoma and squamous cell carcinoma, as well as ovarian, pancreas, and lung carcinomas. In one population-based study, Mirena® increased the risk for breast carcinoma by approximately 20%, whereas a number of other studies failed to demonstrate such a hazard. In the recent decades of the increased predominance of insulin resistance and obesity and an occurrence of hormone-dependent carcinomas at earlier age, a broad application of levonorgestrelreleasing intrauterine systems may become a particularly important component of primary prevention of malignancies in women. Both obese and overweight patients seem perfect candidates for such a hormonal intervention.