Bone densitometry is one of the most frequently used investigations in the assessment and management of patients suspected to have osteoporosis. The current method of choice for measuring BMD is dual-energy X-ray absorptiometry, because of its high precision and low radiation dose. The initiation and choice of treatment in patients with osteoporosis is critically dependent on the availability of BMD measurements and BMD can also be used to monitor the response to therapy. Transiliac bone biopsy is indicated for selected patients with metabolic bone disease where less invasive investigations have yielded inconclusive results. Under these circumstances it is an invaluable investigation that can be used to differentiate infiltrative disorders from primary abnormalities of osteoblast or osteoclast function.