THE PROCESS OF BUILDING EMPIRICAL-STOCHASTIC MODELS OF CRIME OCCURRENCE--MATHEMATICAL STATEMENTS DERIVED FROM HISTORICAL DATA ON THE MONTHLY INCIDENCE OF INDEX CRIMES--IS REVIEWED BRIEFLY. THE CONCEPTUAL APPROACH AND STATISTICAL FORMULATION INVOLVED IN USING THESE MODELS IN AN INTERVENTION ANALYSIS FRAMEWORK (THE COMPARISON OF PROJECTED AND OBSERVED LEVELS OF CRIME OCCURRENCE TO DETERMINE THE EFFECT OF AN INTERVENTION) ARE DESCRIBED. A SENSITIVITY ANALYSIS DEMONSTRATES THE ABILITY OF THE SUGGESTED INTERVENTION ANALYSIS APPROACH TO DETECT, WITH MINIMAL LAPSE OF TIME, SMALL BUT REAL CHANGES ASSOCIATED WITH INTERVENTIONS. INTERVENTION ANALYSIS IS DEMONSTRATED IN AN ASSESSMENT OF THE EFFECTS OF A MASSACHUSETTS LAW MANDATING A 1-YEAR MINIMUM SENTENCE FOR CARRYING A FIREARM WITHOUT A SPECIAL LICENSE. LEVELS OF HOMICIDE, ASSAULT WITH GUN, AND ARMED ROBBERY IN BOSTON BEFORE AND AFTER PASSAGE OF THE LAW IN APRIL 1975 ARE EXAMINED TO DETERMINE THE EFFECTIVENESS OF THE LAW AS A DETERRENT TO CARRYING GUNS AND COMMITTING GUN-RELATED CRIMES. THE ANALYSIS SHOWS A DECREASE IN ASSAULTS AND ROBBERIES A FEW MONTHS PRIOR TO THE OFFICIAL ENACTMENT OF THE LAW BUT NO SIGNIFICANT CHANGE OF HOMICIDE, AT LEAST THROUGH OCTOBER 1975. IT IS POINTED OUT THAT THE SHIFT IN ASSAULT AND ROBBERY LEVELS IS CONSISTENT WITH THE EARLY PUBLICITY GIVEN THE LAW IN THE NEWS MEDIA. IT IS NOTED FURTHER THAT, PERHAPS DUE TO THE LARGE PROPORTION OF HOMICIDES OCCURRING IN HOMES, ANY IMPACT OF GUN CONTROL ON HOMICIDE IN GENERAL MAY NOT BE DETECTED FOR SEVERAL YEARS, IF EVER. GRAPHIC AND TABULAR DATA, MATHEMATICAL FORMULATIONS, AND A LIST OF REFERENCES ARE INCLUDED. (LKM)