Premenstrual Dysphoric Disorder (PMDD) describes the cyclic appearance of affective symptoms and resultant impairment during the luteal phase of the menstrual cycle. The objective of this trial is to determine if extended oral contraceptive (OC) regimens with eliminated pill-free intervals will successfully prevent the expression of PMDD symptoms. The central hypothesis of this application is that continuous administration of OCs will minimize the destabilizing effects of changing reproductive steroid levels and prevent PMDD symptom emergence. The cause of PMDD is unknown, the morbidity substantial, and the identified treatments limited in their effectiveness, since 40% of PMDD women are non-responders to elective serotonin re-uptake inhibitors (SSRIs). Earlier controlled studies of OCs to treat PMDD failed to find OCs superior to placebo using the traditional 21/7 platform (21 active pills followed by a 7 day pill-free interval (PFI)). Two recent trials of a low dose OC using a 24/4 platform did report greater reductions in premenstrual symptoms relative to placebo, presumably due to the shortened PFI. Despite the apparent efficacy of the 3-day extended dosing of this OC, the placebo response rate was substantial in these studies, resulting in a low effect size. Moreover, no steroid hormone levels were examined in these prior studies. In the absence of hormonal data, inferences about the mechanism of efficacy of extended OCs must remain speculative and untested.