To confirm the non-inferiority of 75 mg risedronate tablets taken on 2 consecutive days per month as compared to 5 mg risedronate tablets taken daily in increasing bone mass in lumbar spine in postmenopausal women with osteoporosis.

To confirm the efficacy of 75 mg risedronate tablets taken on 2 consecutive days per month in postmenopausal women with osteoporosis in increasing bone mass in proximal femur, femoral neck and femoral trochanter and decreasing bone resorption.

To confirm general safety of 75 mg risedronate tablets taken on 2 consecutive days per month as compared to 5 mg risedronate taken daily.

Inclusion Criteria:

Subjects meeting all of the following criteria were considered for enrollment into the study :

·Ambulatory, healthy postmenopausal women with :

• Natural menopause and more than 5 years after their last menstrual period.
• Or surgical menopause and more than 5 years after surgery (blood hormone tests required for subjects less than 65 years of age who had uterus removed without removal of ovaries at time of surgery).

Osteoporosis (lumbar spine T-score more than 2.5 SD below the mean value in normal young women or more than 2.0 SD below the mean value in normal young women and at least 1 fracture of a vertebra (thoracic-lumbar T4-L4)).

Exclusion Criteria:

Subjects with any of the following criteria were not considered for enrollment into the study :

·Women who have received hormone replacement therapy (with estrogen by mouth and/or progestogen and/or androgen) or raloxifene, or other bone active drugs, such as calcitonin, calcitriol/calcidiol/alfacalcidol, parathyroid hormone or any bisphosphonate within 3 months before first dose of study medication.