Fractures are a major health problem, occurring in >50% of older women. Low bone density is a strong risk factor for fracture, but 80% of fractures occur in women without low bone density. We have fully recruited a 10 year clinical trial in 1054 women investigating whether zoledronate, an effective treatment for osteoporosis, can be given very infrequently by injection to prevent bone loss and spinal fractures in early post-menopausal women with normal or only mildly low bone density. The first participants completed 3 years of follow-up in June 2015. During the trial, zoledronate or an inactive agent (placebo) is administered every 5 years. The main outcomes are occurrence of new spinal fractures and changes in bone density. If the treatment is effective, the study will offer a new, more convenient approach to preventing fractures, and potentially a much higher proportion of fractures could be avoided than with current strategies.