This is the first book that provides a comprehensive and in-depth account of the current state of knowledge on the ovarian reserve and its clinical applications in gynaecology and reproductive medicine. “Ovarian reserve” is a term commonly used to reflect the total number of remaining primordial follicles, which determines a woman’s fertility potential. Since its emergence in the late 1980s during the early days of assisted reproduction technology, the concept of ovarian reserve has continued to gain importance in clinical practice and research, as reflected by the exponentially growing number of publications on the topic. A wide range of ovarian reserve markers have been introduced over the years, starting with serum follicle stimulating hormone level in 1988 and most recently anti-Müllerian hormone in 2002. This book starts with a detailed background on the physiology of the ovarian reserve including early ovarian development, follicular dynamics, and the natural history of primordial follicles. This is followed by a comprehensive account of the various biochemical, sonographic, and dynamic markers and their current applications. A special chapter is devoted to anti-Müllerian hormone, which is the most extensively researched and widely used ovarian reserve marker. The role of anti-Müllerian hormone and its clinical utility in polycystic ovarian syndrome is presented in a separate chapter. The book then explores the clinical applications of ovarian reserve testing in various reproductive disorders, including early ovarian aging, diminished ovarian reserve (pathological and iatrogenic), poor ovarian response during assisted reproduction technology, and premature ovarian insufficiency.