Secondary osteoporosis is common among patients being evaluated for osteoporosis. All men and premenopausal women with unexplained bone loss or a history of a fragility fracture should undergo a work-up for secondary osteoporosis. Also, postmenopausal women with risk factors for secondary osteoporosis should be carefully evaluated. The evaluation should include a thorough history, physical examination, bone mineral density testing, and laboratory testing. While there is no consensus for a cost-effective laboratory evaluation, some recommendations include: 25-hydroxyvitamin D, parathyroid hormone (PTH), serum and urine calcium, phosphate, creatinine, liver function tests, a complete blood count, testosterone in men, and thyroid-stimulating hormone. After a thorough review of the evaluation for secondary osteoporosis, this chapter reviews the pathophysiology and treatment of secondary osteoporotic disorders, including vitamin D insufficiency, osteomalacia, the osteoporosis of erosive inflammatory arthritis, ankylosing spondylitis, systemic lupus erythematosus, and osteoporosis related to anti-androgenic therapy for prostate cancer and aromatase inhibitor therapy for breast cancer. Physicians have a significant responsibility to evaluate and treat the underlying medical problem that is the cause of secondary osteoporosis and to optimize bone health in the individual patient.