From April 9 through April 11, 1964, some 175 American experts in various aspects of mental retardation met in Chicago under the auspices of the Council on Mental Health and the Committee on Maternal and Child Care of the American Medical Association. Grouped in 14 task forces, these experts discussed and drew up a set of guidelines intended to aid the practicing physician in the prevention, diagnosis, and treatment of mental retardation. From their work stems this handbook, to be distributed widely among the nation's physicians and, it is hoped, to play an important role in a concerted and continuing AMA program toward prevention and improved management in the field of mental retardation. The need for such action is clear. The population of the United States today includes more than 5 million individuals who at some point in their lives have been or will be diagnosed as retarded. As pointed out in the AMA mental health program (available