Chronic anovulation is an important cause of infertility, accounting for approximately 20% of all causes. Men should have had a semen analysis and women should have had the basic infertility work-up including an assessment of tubal patency. In 1973 the World Health Organization published a simple classification of anovulation, namely, WHO I, II and III. WHO I patients are characterized by a history of amenorrhea. WHO II is characterized by a history of oligomenorrhea, although there may be some with amenorrhea. Central obesity is a cardinal feature of women with polycystic ovary syndrome (PCOS) with an increased waist-hip ratio. WHO III is characterized by oligoamenorrhea, and may present with menopausal symptoms, such as hot flushes, night sweats, and vaginal dryness. This chapter presents the treatment for WHO I, II, and III patients. The treatment involves lifestyle modification, aromatase inhibitors, insulin-sensitizing drugs, and hyperprolactinemia.