Increasing evidence suggests that a high rate of bone turnover is associated with low bone mineral density (BMD) and is strongly linked to fracture risk. Measurement of biochemical markers of bone turnover is therefore becoming a more widely used endpoint in clinical trials in postmenopausal osteoporosis. This multinational double-blind, fracture-prevention study enrolled 2946 postmenopausal women with osteoporosis. Patients were randomized to receive placebo or oral ibandronate administered daily (2.5 mg/day) or intermittently (20 mg every other day for 12 doses every 3 months). The primary endpoint was the incidence of new vertebral fractures after 3 years. Secondary outcome measures included changes in the rate of bone turnover as assessed by biochemical markers and increases in spinal and hip BMD. Daily and intermittent oral ibandronate significantly reduced the risk of vertebral fractures by 62% and 50%, respectively, and produced significant and sustained reductions in all the measured biochemical markers of bone turnover. By 3 months, the rate of bone turnover was reduced by approximately 50-60%, and this level of suppression was sustained throughout the remainder of the study. In summary, oral ibandronate, given daily or with a between-dose interval of >2 months, normalizes the rate of bone turnover, provides significant increases in BMD and a marked reduction in the incidence of vertebral fractures. Thus, intermittent ibandronate has potential to become an important alternative to currently licensed bisphosphonates in postmenopausal osteoporosis.