Recently, several methods for measurement of bone density have been developed. Among them, dual X-ray absorptiometry (DXA) is now considered to be a standard method in bone densitometry. In most cases, values by DXA measurement reflect bone strength and thus measurements of lumbar spine and femoral neck by DXA are used for diagnosis of osteopenia or osteoporosis. In several clinical trials of new drugs, measurement of DXA proved to be very useful. Other methods such as DXA for os radius or os calcaneus are also useful for screening of general osteopenia and quantitative ultrasound is widely used for mass-screening of osteoporosis because of its convenience. Radiographic absorptiometry is also a convenient method, which can be performed only by taking an X-ray photograph with an aluminum phantom. Quantitative computed tomography (QCT) is a method which enables measurement of trabecular true bone density as well as an analysis of trabecular structure and peripheral QCT, aimed for measurement of peripheral bones, is also expected to be a sensitive method to monitor therapeutic responses. Since several methods are now available, it is important to choose a method which is the most suitable for the purpose of each bone mineral measurement.