This study is aimed to evaluate efficacy and safety of dienogest 2 mg oral tablets in the treatment of endometriosis.

There will be 2 study phases: a double-blind, randomized, placebo-controlled, parallel-group phase over 24 weeks, and an open-label extension phase with 2 mg DNG daily p.o. over 28 weeks for all subjects who completed the double-blind phase, irrespective of their treatment assignment in the first study phase.

Inclusion Criteria:

• Women between 18 and 45 years of age, inclusive
• Women with endometriosis confirmed by laparoscopy or laparotomy within ten years but no later than 2 weeks before the Screening Visit
• A score of at least 30 on a 100 mm visual analog scale (VAS) for endometriosis-associated pelvic pain at Screening Visit and Baseline Visit
• Good general health (except for findings related to endometriosis, with or without infertility), as evidenced by medical history and complete physical and gynecological examination
• Willingness to use a barrier method of contraception is required

Exclusion Criteria:

• Pregnancy or lactation (less than three months since delivery, abortion, or lactation before start of treatment)
• Wish for pregnancy within intended treatment period
• Before menarche or after menopause
• Amenorrhea (more than three consecutive months in the six months before screening)
• Undiagnosed abnormal genital bleeding
• Previous/use of hormonal agents
• Any disease or condition that may worsen under hormonal treatment
• Signs and/or symptoms of therapy-resistant endometriosis despite more than one prior attempt at drug treatment or surgical therapy
• Need for primary surgical treatment of endometriosis
• Regular use of pain medication due to other underlying diseases
• Contra-indication for the supportive analgesic medication (ibuprofen)