Pain is an important problem for patients with cancer, occuring in half of all cancer patients and more than 90 % of patients with advanced disease. Pain related to cancer is a complex, multidimensional phenomenon composed of sensory, affective, cognitive, and behavioural components. The World Health Organization (WHO) has idendified cancer pain as a major international problem and pain control has become a critical element in the comprehensive care of many cancer patients. Pain and quality of life are phenomena that share several fundamental characteristics. Pain control plays a key role in determining health-related quality of life (HRQOL). Pain, when it is ongoing and uncontrolled, has a detrimental, deteriorative effect on virtually every aspect of a patient's life. It produces anxiety and emotional distress; undermines well-being; interferes with functional capacity; and hinders the ability to fulfill familial, social, and vocational roles. With such broad-based effects, it is apparent that pain would have the effect of diminishing quality of life. In patients with moderate or severe pain, interference with sleep, daily life activities, enjoyment of life, work ability, and social interactions have been reported.