Ovarian reserve is defined as the number of oocytes remaining in the ovary, or oocyte quantity (oocyte number). Markers of ovarian reserve include hormone levels and sonographically measured features of the ovaries. These markers can be useful as predictors of oocyte yield following controlled ovarian stimulation and oocyte retrieval. However, they are poor predictors of reproductive potential independently from age. This document replaces the document of the same name last published in 2012 (Fertil Steril 2012;98:1407–15).