Pain physicians do not treat all diseases. Pain physicians treat primarily patients with chronic pain. For many chronic pain patients, pain itself is the disease. For example, for patients with migraine and trigeminal neuralgia, a cure for pain is a cure for disease. A common phrase among cancer patients is, “I am not afraid of death, but of pain”, and “the pain is unbearable” is the most accurate description. As human life expectancy increases, the occurrence of pain becomes more common: for example, neuropathic pain caused by diabetes mellitus; post-herpetic pain caused by reduced resistance to herpes zoster, which causes severe pain even with clothing contact; low back pain caused by disc herniation, spinal stenosis, and osteoporosis, etc. Treating these chronic pains is the specialty of pain physicians. The following pain clinical comprehensive classification diseases have been basically cured after the treatment of the relevant disciplines of the underlying disease, but the patient still can not relieve pain, can be treated in the pain department. 1.Headache: cervicogenic headache; tension headache; migraine; cluster headache; post-traumatic headache of vascular origin. 2.Maxillofacial pain: trigeminal nerve and its branches pain; linguopharyngeal neuralgia; pteropalatine neuralgia; facial organogenic pain. 3.Collar and occipital pain: occipital neuralgia; mastoid pain; myofascial pain in the cervical region. 4.Cervical and shoulder pain: cervical arthropathy; neck and shoulder syndrome; atlanto-occipital deformity; cervical rib; frozen shoulder. 5.Upper limb pain: upper limb vascular pain; humeral epicondylitis, tenosynovitis; anterior oblique muscle syndrome; thoracic outlet syndrome. 6, chest pain: intercostal neuralgia; post-herpetic neuralgia; intercostal neuralgia after chest surgery; costochondritis; intrathoracic organ disorders invade chest wall neuralgia. 7, abdominal pain: abdominal wall neuralgia; abdominal wall phlebitis; post-surgical incision pain. 8, low back pain: pain after nerve injury; phantom limb pain; residual limb pain; complex local pain syndrome; failed spinal surgery syndrome; rheumatoid rheumatic pain; ankylosing spondylitis low back pain; fibromyalgia; erythema limb pain; gouty arthritis; lower limb ischemic pain; peripheral neuritis; achalgia. 9.Central pain: pain caused by stimulation from the spinal cord, brainstem, thalamus, and cerebral cortex. 10.Psychogenic pain: there is no clear lesion or tissue damage but the patient feels persistent pain. 11.Cancer pain. 12.Non-painful diseases: intractable eruption, facial nerve palsy, facial muscle spasm, indeterminate statement syndrome. The scope of practice of pain medicine is mainly chronic pain treatment.