Measures of ovarian reserve, particularly anti-Müllerian hormone, have been increasingly and inaccurately utilized as "fertility tests." It is important to understand the available measures of ovarian reserve and how to appropriately interpret and integrate their use into clinical practice. The objectives of this article are to review the process of reproductive aging, define ovarian reserve, describe the available measures of ovarian reserve, and discuss the clinical utility of these measures. A literature search was performed using the electronic database PubMed. Relevant guidelines, systematic reviews, and original research articles investigating ovarian reserve parameters and their clinical utility were reviewed. The fecundity of women gradually declines with increasing reproductive age as oocyte quantity and quality decline. Ovarian reserve is defined as the quantity of oocytes remaining in the ovary. Ovarian reserve can be measured indirectly with the use of serum blood tests or ultrasound imaging. Measures of ovarian reserve are clinically useful in several circumstances, particularly for use during fertility treatment and cycles of assisted reproductive technology. However, measures of ovarian reserve are poor predictors of reproductive potential and should not be used as "fertility tests." Measures of ovarian reserve are poor predictors of reproductive potential and should not be used as "fertility tests." Age remains a stronger predictor of reproductive success than measures of ovarian reserve.