Osteoporosis is a diffuse skeletal disease in which a decrease in bone strength leads to an increased risk of fractures. A wide variety of types of bone densitometry measurements are available, including quantitative computed tomography measurements of the spine, quantitative ultrasound devices for measurements of the heel and other peripheral sites and dual-energy X-ray absorptiometry (DXA) for measurement of bone mineral density (BMD) at the lumbar spine, proximal femur, forearm and total body scans. Compared with alternative bone densitometry techniques, hip and spine DXA examinations have a number of advantages that include a consensus that BMD results can be interpreted using the World Health Organization T score definition of osteoporosis, a proven ability to predict fracture risk, proven effectiveness at targeting anti-fracture therapies, and the ability to monitor response to treatment. However, in recent years, the authors have raised some important questions about the objective limits of this method that have led to doubts about its effectiveness in terms of clinical outcome.