By 1905 Spiller1had conceived of an isolated tract in the spinal cord mediating pain. In 1911 Martin,2at Spiller's suggestion, did the first chordotomy to relieve pain. This operation, which has come to be known as the Spiller-Frazier operation, or, more commonly, as chordotomy, has been done many times since its introduction, and numerous reports have testified to its efficacy and value. In doing 41 chordotomies during the past three years, one of us (O. H.) saw reason to question the accepted location of the spinothalamic tract as well as the accepted disposition of its fibers. We are reporting 6 cases in which the operation was done with the patient under local anesthesia only. Sections were made in the cord according to various patterns, and cutaneous sensibility was tested at the operating table. GENERAL FACTORS RELATED TO CHORDOTOMY Segment of Election. —The most popular locations for section