This chapter discusses menstrual disorders such as abnormal uterine bleeding (AUB), amenorrhea, dysmenorrhea, and premenstrual syndrome (PMS). AUB is a variation from a patient’s usual menstrual pattern, including postmenopausal bleeding. Amenorrhea such as primary amenorrhea is a failure of the menses to occur by age 15. Secondary amenorrhea is a cessation of the menses for longer than 6 months (or for three consecutive cycles) in a patient who has established menses at least 1 year after menarche. Dysmenorrhea such as primary dysmenorrhea is the occurrence of painful menses. Secondary dysmenorrhea is painful menstruation due to an identifiable pathologic or iatrogenic condition. PMS is a cluster of physical, emotional, and behavioral symptoms related to the menstrual cycle, developing or worsening during the luteal phase and clearing with the onset of the menstrual flow. This chapter discusses the etiology, history, physical examination, differential diagnosis, laboratory testing, treatment and intervention, complications, consultation/referral, and follow-up for menstrual disorders.