Bone densitometry is currently widely recommended for, and considered central to, identifying post-menopausal women and older men at high risk of fracture and establishing an indication for pharmacological fracture-prevention therapy. The purpose of this article is to comprehensively review cost-effectiveness modelling studies published to date of bone mass measurement technologies (primarily dual energy x-ray absorptiometry [DXA]) designed to identify those individuals at sufficiently high risk of fracture to warrant pharmacological fracture-prevention therapy. Based on older paradigms of the pharmacological treatment of those with a bone density value below a specific threshold, bone densitometry appears to be cost effective for post-menopausal women aged > or =65 years, regardless of the presence or absence of other clinical risk factors. For younger post-menopausal women, bone densitometry is likely to be cost effective only for those with specific clinical risk factors, such as prior fracture or low bodyweight. For older men, bone densitometry may be cost effective for those who have had a prior fracture and/or are aged > or =80 years, but the subset of men for whom bone densitometry is likely to be cost effective may vary from country to country depending on societal willingness to pay for health benefits, fracture rates in the population and the costs of bone densitometry and drug treatment. The cost effectiveness of other technologies such as heel ultrasound, peripheral DXA and quantitative CT remains uncertain. However, in the context of the new WHO paradigm of directing treatment based on absolute fracture risk rather than bone density, a new generation of cost-effectiveness modelling studies will be required to define the most cost-effective way bone densitometry can be used to identify those who are likely to benefit sufficiently from pharmacological fracture-prevention therapies.