Normal menstruation is the end product of a complex interplay of health and hormones. This chapter discusses the etiology, treatment and evaluation of amenorrhea, polycystic ovary disease and abnormal menstrual bleeding. Many of the causes of amenorrhea can also cause oligomenorrhea, metrorrhagia, menorrhagia, and other irregularities of menstruation. Primary amenorrhea occurs in adolescents who have never had a menstrual period. Women with amenorrhea can be placed on ovulation inducing drugs. An ovulation inducing agent, such as clomiphene is needed. Metformin may be used in those women with polycystic ovarian syndrome (PCOS). Metformin improves the endocrine symptoms of PCOS, even in women who are not diabetic. It treats insulin sensitivity, induces normal ovulatory cycles, and causes weight loss, although this is an off-label use. Heavy menstrual bleeding (HMB) is an important cause of ill health in women.