Purpose of investigation: The appropriate time for patients to discontinue dienogest (DNG) after long-term use has been a recent topic of debate. Therefore, this study evaluated the timing for discontinuation of DNG in climacteric patients suffering from endometriosis and adenomyosis. Materials and Methods: DNG was orally administered at 2 mg/day for more than 12 months. The serum estradiol (E2) and follicle-stimulating hormone (FSH) levels were measured every three to six months. DNG was discontinued when the hormone levels changed to those characteristic of menopause. Results: FSH levels in three patients increased to more than 25.8 mIU/mL during DNG administration. They were thus diagnosed as having entered menopause. There was no recurrence of pain in these patients at one year after discontinuation of DNG. Conclusion: An increase in serum FSH levels could help in confirming the diagnosis of menopause. In addition, DNG prevented the recurrence of endometriosis and adenomyosis.