The bone is a frequent site for tumor metastasis, and cancer in the bone results in marked disturbances of bone remodeling that can be lytic, blastic or a combination of the two. Patients with advanced malignancies that have metastasized to the bone frequently suffer from debilitating skeletal-related events, including pathologic fractures, spinal cord compression syndromes, disorders of calcium and phosphate homeostasis and severe cancer-related pain. This review will discuss recent studies on the mechanisms responsible for osteolytic and osteoblastic metastasis and how their identification has resulted in the development of new agents for patients with metastatic bone disease.