OBJECTIVE: The XIST gene is considered to be an attractive candidate gene for skewed X-chromosome inactivation and a possible cause of primary ovarian insufficiency (POI). The purpose of this study was to investigate whether the XIST gene promoter mutation is associated with idiopathic POI in a sample of the Korean population. METHODS: Subjects consisted of 102 idiopathic POI patients and 113 healthy controls with normal menstrual cycles. Patients with the following known causes of POI were excluded in advance: cytogenetic abnormalities, prior chemo- or radiotherapy, or prior bilateral oophorectomy. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS: The mean age of onset of ovarian insufficiency was 28.7+/-8.5 years and the mean values of serum luteinizing and follicle-stimulating hormones and estradiol in the POI group were 31.4+/-18.2 mIU/mL, 74.5+/-41.1 mIU/mL, and 30.5+/-36.7 pg/mL, respectively. We found no cytosine to guanine (C43G) variation in the XIST gene in both POI patients and controls. CONCLUSION: The C43G mutation in the promoter region of the XIST gene was not present in the Korean patients with idiopathic POI in our study, in contrast to our expectation, suggesting that the role of XIST in the pathogenesis of POI is not yet clear.