**Abstract**

The human ovary is a complex structure that is controlled by endocrine, paracrine, and autocrine mechanisms. The number of eggs retrieved after controlled ovarian stimulation in in vitro fertilization depends on the physiological follicular reserve pool of ovaries. Ovarian reserve is decided genetically and decreases with advancing age and gets affected by ovarian surgery, chemotherapy, radiotherapy, and autoimmune disorders. Environmental influences like chronic smoking, hyperglycemia, and conditions interfering ovarian vascularity also reduce the ovarian reserve. This chapter summarizes the methods to assess the ovarian reserve. This helps in deciding the initiating dose of gonadotropins for controlled ovarian hyper stimulation for optimal follicular response.

**Keywords:** ovary, controlled ovarian hyper stimulation, in vitro fertilization, ovarian reserve, ovulation
