It is estimated that 50–80% of menstruating women experience some degree of physical and psychological premenstrual symptomatology and that 3–5% have symptoms of sufficient severity to disrupt social or psychological functioning. The diagnosis of clinically significant premenstrual syndrome (PMS) is applicable when at least one moderate to severe physical and psychological symptom occurs for up to two weeks prior to menses with remission by the end of the menstrual flow. Symptoms should cause functional impairment and must be documented prospectively for at least two consecutive menstrual cycles. Table 1 lists the American College of Obstetrics and Gynecology (ACOG) criteria set for the diagnosis of PMS.