THE FOLLOWING SETS OF INFORMATION WERE COLLECTED: 1975 STATISTICS ON THE LAW'S IMPACT ON THE ILLEGAL CARRYING OR POSSESSION OF FIREARMS; BOSTON POLICE DEPARTMENT MONTHLY VIOLENT CRIME INCIDENT REPORTS COVERING THREE YEARS BEFORE AND ONE YEAR AFTER THE LAW'S EFFECTIVE DATE OF APRIL 1, 1975; AND DATA ON PROSECUTIONS FOR FIREARM CRIME THAT ENTERED THE BOSTON LOWER COURT SYSTEM DURING APRIL THROUGH SEPTEMBER OF 1975. FINDINGS REVEALED THAT MOST OF THE DIRE PREDICTIONS ABOUT POLICE, PROSECUTORIAL, AND JUDICIAL EVASION OF THE LAW WERE NOT PROVEN ACCURATE, THAT THE MANDATORY MINIMUM DID NOT ADD TO THE LIKELIHOOD THAT THOSE ACCUSED OF HOMICIDE OR ARMED ROBBERY WOULD RECEIVE PRISON SENTENCES, AND THAT FIREARM CHARGES COULD ONLY BE USED IN ABOUT ONE FOURTH OF ALL PROSECUTIONS FOR VIOLENT CRIMES ALLEGEDLY INVOLVING FIREARMS. NEVERTHELESS LOWER COURT JUDGES DID APPEAR TO BE APPLYING THE MANDATED PENALTY. A RADICAL INCREASE IN COMPLIANCE WITH THE LAW REQUIRING FIREARMS PERMITS AND LICENSE WAS NOTICED, AND CRIME STATISTICS FOR THE YEAR AFTER THE LAW TOOK EFFECT SHOWED A REDUCTION IN THE USE OF FIREARMS IN ASSAULTS.