One of the most common difficulties in treating cancer is pain. Pain can be associated with both localized tumors and metastatic cancer. Although only 15% of patients with nonmetastatic disease had pain associated with their tumor at the time of diagnosis, pain becomes more pervasive as disease progresses. With the diagnosis of metastatic disease the percentage of patients having pain increased to 74%. Direct tumor involvement is the most common cause of pain, present in approximately two thirds of patients with pain from metastatic cancer. Tumor invasion of bone, common in breast and prostate cancer and with multiple myeloma, accounts for pain in approximately 50% of these patients. The remaining 50% experience tumor-related pain that is due to nerve compression or infiltration, or tumor involvement of the gastrointestinal tract or soft tissue.