The evidence is strong that bimedial lobotomy is superior in treatment of chronic mental illness to either conventional bilateral lobotomy or unilateral lobotomy. The reduction in anxiety, tension, hostility, and impulsivity is dramatic; the improvement in initiative and ability to form object relationships, the increased capacity to work and to get along, the recession of psychotic symptoms—all were most significant and important. In group situations, patients who received bimedial operation were more interested in interaction, more alive to group needs, more productive and organized in their activities than patients receiving the other operations. Psychological tests suggest that they made definite gains in abstraction capacity. There was no mortality in the total series of cases. The immediate postoperative morbidity of bimedial surgery was no greater than other operations and the incidence of untoward complications no greater than for conventional bilateral lobotomy.For the present, at the Boston Psychopathic Hospital, bimedial lobotomy has replaced standard full bilateral operation in surgical treatment of chronic mental illness.