In assisted reproductive technology (ART) treatments, the ovarian stimulation method is important for obtaining many good quality oocytes. The first ovarian stimulation treatments used high stimulation in long and short protocols with gonadotropin releasing hormone (GnRH) agonists. It was formulated to suppress the luteinizing hormone (LH) surge while the follicles are developing. Subsequently, a moderate stimulation with an antagonist was introduced following the development of GnRH antagonists, and low stimulation that inhibits the LH surge with continuous administration of clomiphene citrate. However, cases have been reported occurred in which estrogen replacement therapy was selected to facilitate follicular development by supplementing estrogen in ovarian insufficiency. Otherwise ART cryopreservation technology has also developed. These practices are referred to as oncofertility, and have given rise to new ovarian stimulation methods in infertility treatment. Ovarian stimulation with the random start or double stimulation methods, which are not readily affected by the menstrual cycle, and progestin-primed ovarian stimulation (PPOS) that inhibits the LH surge with a progestogen have come to be performed and are showing good outcomes. As the social and medical backgrounds change, the methods of ovarian stimulation may futher improve in the future.