KLINEFELTER' SYNDROME IS CHARACTERIZED BY TESTICULAR TUBULAR FIBROSIS, DEVELOPMENT OF FEMALE BREASTS, AND ELEVATED EXCRETION OF THE SUBSTANCE THAT REGULATES THE ACTIVITY OF THE TESTES. KLINEFELTER'S SYNDROME IS ALSO ASSOCIATED WITH THE PRESENCE OF POSITIVE (FEMALE) CHROMATIN--THE SUBSTANCE OF THE CELL NUCLEUS THAT FORMS CHROMOSOMES UPON CELL DIVISION. THE SYNDROME MAY BE ETIOLOGICALLY RELATED TO MONGOLISM AND TO TWINNING. A COMPARISON BETWEEN 10 MENTALLY DEFICIENT MALE PATIENTS WITH CHROMATIN-POSITIVE KLINEFELTER'S SYNDROME AND A CONTROL GROUP CONSISTING OF ALL MALES ADMITTED TO A STATE HOSPITAL FROM 1948 TO 1952 SHOWS A SIGNIFICANTLY HIGHER INCIDENCE OF SEXUALLY DEVIANT BEHAVIOR AMONG THE KLINEFELTER PATIENTS -- AN INDICATION THAT PERSONALITY DISTURBANCE IN KLINEFELTER PATIENTS MAY DIFFER QUALITITATIVELY FROM THAT IN OTHER PATIENTS. A SURVEY OF 600 INSTITUTIONALIZED MALE SEXUAL PSYCHOPATHS FOUND THAT 6 (1 PERCENT) WERE CHROMATIN-POSITIVE. THIS INCIDENCE IS ABOVE THAT IN THE GENERAL POPULATION, BUT MAY REFLECT CERTAIN SOCIAL FACTORS TENDING TO FAVOR COMMITMENT OF MEN WHO EXHIBIT ABNORMALITIES FOUND IN KLINEFELTER'S SYNDROME. (FOR INSTANCE, THESE MEN ARE INFERTILE AND MAY BE LESS LIKELY TO BE SHOWN LENIENCE BY THE COURTS THAN ARE FATHERS.) IT IS URGED THAT CHROMATIN TESTING BE DONE ON YOUNG BOYS WITH MENTAL DEFICIENCIES OR SERIOUS PERSONALITY OR BEHAVIORAL DISTURBANCES, ESPECIALLY FOR BOYS WITH MONGOLOID OR TWIN SIBLINGS. SUPPORTING DATA AND A LIST OF REFERENCES ARE INCLUDED. (LKM)