This is a comprehensive study which reports on bilateral leucotomy, bilateral lower quadrant leucotomy, unilateral leucotomy, and orbital gyrectomy for the relief of pain. Six patients who had undergone bilateral leucotomy had severe psychological changes (i.e., deterioration of behavior, impaired judgment) immediately after operation but with some later improvement. Apathy was the predominant feature noted in nine patients following bilateral lower quadrant leucotomy. Slight changes—flattening of affect, inappropriate affect, decrease in the rate of speech in words per minute, and increase in the time interval prior