EARLY STUDIES DURING THE 1960'S, BOTH IN THE U.S. AND ABROAD, POINTED TO A CONNECTION BETWEEN THE PRESENCE OF A 47TH CHROMOSOME IN SELECTED MALES AND THEIR CONSISTENT ANTISOCIAL BEHAVIOR. THE FEATURES OBSERVED AMONG XYY INDIVIDUALS INCLUDED AGGRESSIVE BEHAVIOR, MENTAL DEFICIENCY, AND TALLNESS; THE IMPRESSION IMMEDIATELY PREVAILED THAT THESE CHARACTERISTICS WERE RELATED TO THE POSSESSION OF A DOUBLE DOSE OF THE GENETIC MATERIAL PRESENT IN THE Y CHROMOSOME. THE IMPACT OF THESE OBSERVATIONS, ALTHOUGH STILL RESTRICTED TO SCIENTIFIC CIRCLES, WAS EXPECTEDLY CONSIDERABLE, AND IT SEEMS THAT A NUMBER OF HUMAN CYTOGENETICISTS WONDERED AT THE TIME OF JULY 1966 MASS MURDER IN CHICAGO WHETHER THE SUSPECT IN THE CASE DID NOT FALL NATURALLY INTO THE DOUBLE YY CLASS OF 'SUPERMALES' DESCRIBED ONLY MONTHS EARLIER IN SCIENTIFIC PUBLICATIONS. HOWEVER, DESPITE A LATER STUDY THAT SHOWED THE SUSPECT'S CHROMOSOME STRUCTURE TO BE PEFECTLY NORMAL, PRESS REPORTS AT THE TIME OF THE MAN'S TRIAL AND CONVICTION ON MURDER CHARGES CONSISTENTLY LABELED HIM AS AN XYY'ER, A MISREPRESENTATION THAT PREVAILED THROUGHOUT THE LENGTHY APPEALS AND THAT EVENTUALLY SPILLED OVER INTO THE SCIENTIFIC PRESS. DESPITE THE PUBLIC RELEASE OF REPEATED CHROMOSOME TEST RESULTS, MAGAZINES CONTINUED TO COMMENT ON HIS CHROMOSOME ANOMALY, SCIENTISTS STILL REFERRED TO IT AT MEETINGS, AND MEDICAL TEXTBOOKS ADOPTED IT AS A NOTABLE CASE. AS FOR THE XYY INFLUENCE ON BEHAVIOR AND CRIME, LATER RESEARCH HAS SHOWN IT TO BE AN EVEN MORE TANGLED ISSUE. A 1970 STUDY OF 190 CONVICTED LIFE TERM CRIMINALS IN TENNESSEE UNCOVERED NOT A SINGLE XYY, A FINDING WHICH UNDERSCORES THE NEED FOR MORE INTENSE STUDIES, POSSIBLY PITTING XYY INFANTS AGAINST XY CONTROLS IN A LIFE LONG COMPARISON OF DEVIANCE AND AGGRESSIVENESS. REFERENCES AND ILLUSTRATIONS ARE INCLUDED. (KBL)