An objective of improvement of treatment outcomes of cancer is alleviation of bone metastasis that occurs in many types of cancers. Recently, the guidelines for the diagnosis and treatment of bone metastasis were published by the Japanese Society of Medical Oncology in cooperation with other groups. These guidelines are essentially evidence based for the pharmacological treatment of bone metastasis by using bone modifying agents (BMA). Cancer cells inhibit osteoblast formation and promote osteoclast proliferation. Many growth factors that are produced by the bone marrow promote osteoclast proliferation. Furthermore, many growth factors enhance the rate of cancer cell growth. These processes underlie bone metastasis. Evidence for the effectiveness of BMA for the treatment of lung cancer, breast cancer, prostate cancer, multiple myeloma, and other cancers is provided in each section of the guidelines. These guidelines also provide evidence for the suppression of skeletal related events (SRE) in lung, breast, and prostate cancers. With regard to multiple myeloma, the guidelines provide evidence for the improvement of overall survival in addition to that for suppression of SRE. Based on these evidences, the guidelines recommend aggressive treatment with BMA for bone metastasis in such cancers.