Excessive menstrual bleeding describes the clinical problems of heavy menstrual blood loss together with frequent or irregular menstruation. This chapter addresses endometrial morphology, the mechanism of menstruation and the aetiology and management of menstrual problems. A very common cause relates to ovulatory dysfunction, which typically leads to a combination of irregular bleeding and a variable volume of menstrual flow, which can lead to heavy menstrual bleeding (HMB). Clotting disorders such as von Willebrand's disease are another cause of HMB. Reduced clotting is a known feature at the time of menstruation. Pelvic pathologies such as fibroids are common, affecting between 20 and 25% of women. It is reported that around a third of women with fibroids complain of heavy menstrual blood loss. There are a number of terminologies to describe menstrual complaints such as menorrhagia, polymenorrhoea, oligomenorrhoea, polymenorrhagia and metrorrhagia.