Osteoporosis appears to be more aggressive, and progress more quickly, than many clinicians previously thought, according to new data released during the UK National Osteoporosis Society's (NOS) Conference [Bath, UK; April 2000]. Delegates also heard that risedronic acid [risedronate; 'Actonel'] is the first osteoporosis treatment proven to reduce fracture risk within this period in a large group of patients. In light of recent question marks concerning the cardiovascular benefits of hormone replacement therapy (HRT), a leading specialist suggests that the findings might redefine the relative roles of current antiosteoporosis treatments.