BACKGROUND Endometrial carcinoma is the most common gynaecologic malignancy in the world and develops through preliminary stages of endometrial hyperplasia. Typical endometrial hyperplasia suggests a significant pre-malignant state with frank progression to endometrial carcinoma. Because atypical endometrial hyperplasia tends to occur at a young age, it has become increasingly important and necessary to find a safe and effective fertility-sparing treatment with better tolerability and fewer side effects than the options for treatment that are currently available. The levonorgestrel-releasing intrauterine system has already been used to provide endometrial protection in women with breast cancer who are on adjuvant tamoxifen. The antiproliferative function of levonorgestrel is thought to reduce the risk of endometrial hyperplasia. OBJECTIVE To determine the efficacy and safety of the levonorgestrel-releasing intrauterine system in reversing atypical endometrial hyperplasia. METHODS In November 2012 we searched the Cochrane Menstrual Disorders and Subfertility Review Group Specialised Register; Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library; MEDLINE; EMBASE; and the China National Knowledge Infrastructure for relevant trials. Attempts were made to identify trials from references in published studies. We also searched for ongoing trials in five major clinical trials registries. METHODS Randomised controlled trials (RCTs) of the levonorgestrel-releasing intrauterine system (LNG-IUS) versus progestin therapy in women with a confirmed histological diagnosis of simple or complex endometrial hyperplasia with atypia. METHODS No eligible study was found. RESULTS We did not identify any studies which met our full inclusion criteria. CONCLUSIONS There is no evidence available from randomised controlled trials regarding the efficacy and safety of the levonorgestrel-releasing intrauterine system (LNG-IUS) for atypical endometrial hyperplasia. RCTS are required to determine whether the LNG-IUS is safe and effective for treating atypical endometrial hyperplasia.