Osteoporosis is an important complication of androgen-deprivation therapy (ADT) for prostate cancer. ADT by either bilateral orchiectomies or treatment with a gonadotropin-releasing hormone (GnRH) agonist decreases bone mineral density (BMD)and increases the risk of fracture. Prospective data about treatment or prevention of osteoporosis in men with prostate cancer are limited. Supplemental calcium and vitamin D are recommended. Additional therapy may be warranted for men with osteoporosis or fractures. Intravenous pamidronate prevents bone loss in the hip and spine during ADT. Intravenous zoledronic acid not only prevents bone loss but also increases BMD. Alendronate is approved to treat men with osteoporosis although the efficacy of alendronate or other oral bisphosphonates has not been evaluated during ADT. Additional prospective studies are needed to evaluate the long-term effects of bisphosphonates and other therapies on fracture risk and disease-related outcomes.