As advances in cancer detection and treatment have increased the life expectancy of cancer patients, more attention to improving patient's quality of life (QOL) is needed. Among symptoms accompanying cancer, pain has strong impact on QOL. Most of cancer patients will experience moderate to severe pain and/or neuropathy during the course of their disease. Cancer pain can arise from different processes, either by direct tumor infiltration/involvement, or toxicity relating to chemotherapy used to treat cancer. The World Health Organization (WHO) has proposed a structured approach to drug selection for cancer pain, known as the "WHO analgesic ladder". However, several types of pain including bone cancer pain and chemotherapy-induced painful peripheral neuropathy are difficult to treat. The development of optimal analgesics for cancer pain has been hampered by the lack of understanding basic mechanisms that contribute to cancer pain. Recently, preclinical models of bone cancer pain and paclitaxel-induced painful peripheral neuropathy have been developed. These models have begun to provide insight into the mechanisms by which cancer pain is induced and how cancer pain-related sensory information is processed. In this paper, we review mechanism of cancer pain.