The levonorgestrel intrauterine system (LNG-IUS), originally designed for long-term contraceptive use, has been on the Scandinavian market for approximately 20 years. Novel clinical indications for the LNG-IUS, derived mainly from investigator-initiated studies, are emerging. These include heavy menstrual bleeding associated with uterine fibroids, endometriosis, adenomyosis, as well as endometrial hyperplasia. In both cohort and randomized studies, the LNG-IUS is effective in decreasing heavy menstrual bleeding, also in women diagnosed with uterine fibroids. In randomized studies the LNG-IUS has shown comparable clinical efficacy to GnRH analogues or progestins for the symptomatic treatment of endometriosis. Experience with LNG-IUS in adenomyosis is based on prospective cohort studies. Dysmenorrhea has been reported to decrease in all women, and uterine volume was seen to diminish in some of these studies. In the treatment of endometrial hyperplasias, including atypical hyperplasia, the LNG-IUS is equal or superior to treatment with systemic progestins. Further studies are needed to examine the full potential of the LNG-IUS in such common clinical situations.