The purpose of this study is to determine whether Levonorgestrel/Ethinyl Estradiol (LNG/EE) is effective in treating the symptoms of severe Premenstrual Dysphoric Disorder.

Inclusion Criteria:

• Generally healthy, women aged 18 to 49 years.
• History of severe PMS symptoms over the last year, as determined by the investigator.
• Regular 21 to 35 day menstrual cycle for 2 months prior to first study visit.

Exclusion Criteria:

• Major depressive disorder requiring antidepressant treatment or hospitalization within the last 3 years.
• Contraindication to combination oral contraceptives.
• Use of antidepressants/anxiolytics within 10 days of screening and for the duration of the study.

Other exclusion applies.