ACCURATE interpretation of pain in the presence of paraplegia presents a challenging problem. Essentially two types of pain occur when the spinal cord has been severely traumatized: root pain and vascular pain.1The latter appears intermittently with varying degrees of severity in almost all paraplegic patients. Surgical therapy for this type of pain has been ineffectual, although at first sympathectomy was viewed with hopefulness. On the other hand, it is desirable to treat the root type of pain surgically and early if addiction to drug and alcohol is to be prevented and proper rehabilitation of the patient is to be achieved. Experiences at this clinic2indicate that lateral spinothalamic tractotomy is the operative treatment of choice in the presence of unquestioned root pain below the fifth thoracic dermatome. It is the purpose of this communication to present evidence fortifying the value of threshold studies and their application in