Ovarian reserve means the functional potential of the ovary and implies the number of oocytes in the ovaries. Diminished ovarian reserve refers to those groups of women of reproductive age who may have regular cycles but may still show reduced fecundity and decreased response to ovarian stimulation. It can refer to diminished oocyte quality, oocyte quantity, or reproductive potential. The identification of poor reserve is an important component of the initial infertility evaluation as more and more patients are presenting for diagnostic evaluation later in their reproductive lifespan. This chapter covers the assessment of ovarian reserve—tests, anti-mullerian hormone and antral follicle count, follicle-stimulating hormone receptor polymorphism, and in vitro fertilization options for poor ovarian responders.