Tibolone has been registered for the treatment of climacteric symptoms and for the prevention of postmenopausal osteoporosis. This is a 2-year study to further confirm the endometrial safety of tibolone in comparison with CE/MPA.

Inclusion Criteria:

• Healthy postmenopausal women, 45 to 65 years of age with an intact uterus. Women must have been postmenopausal for less than 15 years, have an atrophic or inactive endometrium, and a body mass index of 18 - 32 kg/ m2 (inclusive).

Exclusion Criteria:

• Final diagnosis of the endometrial biopsy as 'no tissue' or 'tissue insufficient for diagnosis'.
• Double layer endometrial thickness > 6 mm as assessed by transvaginal ultrasonography (TVUS).
• Any previous or current unopposed estrogen administration or tamoxifen citrate.
• Any unexplained vaginal bleeding following the menopause.
• Women with abnormal Pap smear test results (PAP IIb and higher)
• Previous use of raloxifene hydrochloride for longer than one month.