IN APRIL 1975, MASSACHUSETTS FORMALLY IMPLEMENTED THE BARTLEY-FOX LAW, WHICH MANDATES A 1-YEAR MINIMUM PRISON TERM FOR THE UNLICENSED CARRYING OF A FIREARM. AN EXAMINATION OF THE LAW'S IMPACT ON MASSACHUSETTS' CRIME INDICATES THAT OFFENDERS ADAPTED THEIR PATTERNS OF WEAPONS CARRYING TO THE NEW LAW. THE LAW ENCOURAGED NONGUN, ARMED ASSAULTS, PERHAPS BECAUSE IT DID NOT KEEP OFFENDERS AWAY FROM ASSAULTIVE SITUATIONS. THE LAW ALSO ALTERED CITIZENS' CRIME REPORTING BEHAVIOR BY ENCOURAGING THE REPORTING OF LESS SERIOUS FORMS OF GUN ASSAULTS. ALTHOUGH THE LAW'S DISPLACEMENT EFFECTS (REPLACEMENT OF SPECIFIC CRIMES BY CRIMES THAT DIFFER IN FORM, ETC) SEVERAL EXTERNAL FACTORS MAY HAVE CONTRIBUTED TO THE RISE IN NONGUN-RELATED CRIME. THE DISPLACEMENT EFFECTS OF BARTLEY-FOX LAW WERE LESS CONSISTENT FOR ROBBERY THAN FOR ASSAULT, AND BY 1977, A SHIFT BACK TO THE USE OF GUNS FOR MANY TYPES OF ROBBERIES HAD OCCURRED. THE TREND TOWARDS NONGUN ASSAULTS AND THE DECREASE IN GUN HOMICIDES INDICATE A SHIFT TOWARD LESS POTENTIALLY HARMFUL FORMS OF CRIME. HOWEVER, FURTHER RESEARCH IS REQUIRED TO DETERMINED IF THE THREAT OF PUNISHMENT OR THE ACTUAL IMPOSITION OF PUNISHMENT WAS RESPONSIBLE FOR THE CHANGING PATTERNS OF CRIME IN MASSACHUSETTS. ANALYSIS AND SPECIFIC DISCUSSION CONCERN THE EFFECTS OF THE LAW IN BOSTON AND THE METHODOLOGY OF THE RESEARCH. TABULAR DATA AND REFERENCES ARE PROVIDED. (TWK)