Osteoporosis is an important complication of androgen deprivation therapy for prostate cancer. Androgen deprivation therapy either by bilateral orchiectomies or treatment with a gonadotropin-releasing hormone agonist decreases bone mineral density (BMD) and increases the risk of fracture. Dietary factors and lifestyle may contribute to bone loss. There are limited prospective data about treatment or prevention of osteoporosis in men with prostate cancer and many recommendations are based on studies of postmenopausal osteoporosis. Lifestyle modification including smoking cessation, moderation of alcohol consumption, and regular weight bearing exercise should be encouraged. Supplemental calcium and vitamin D are recommended. Additional treatment may be warranted for men with osteoporosis, fractures, or high rates of bone loss during androgen deprivation therapy. Recent studies have evaluated the efficacy of bisphosphonates to prevent bone loss during androgen deprivation therapy. Pamidronate (pamidronic acid), a second-generation bisphosphonate, prevents bone loss in the hip and spine during androgen deprivation therapy. Zoledronic acid, a more potent third-generation bisphosphonate, not only prevents bone loss but also increases BMD in the hip and spine. Alendronate (alendronic acid) is approved for the treatment of osteoporosis in men although its efficacy and that of other oral bisphosphonates has not been evaluated in men receiving androgen deprivation therapy. Additional prospective studies are needed to evaluate the long-term effects of bisphosphonates on fracture risk and disease-related outcomes.