MULTNOMAH COUNTY IN OREGON REQUIRES THAT ALL PERSONS WHO HAVE SECURITY ALARM SYSTEMS OBTAIN PERMITS FOR THEIR OPERATION. PERMIT RECORDS FROM MAY 1977 TO MAY 1978 PROVIDED A DATABASE OF OVER 5,000 SYSTEMS THAT WAS USED IN DETERMINING THE NUMBER AND TYPE OF ALARM INSTALLATIONS, MOST OF WHICH WERE OWNED BY COMMERCIAL ESTABLISHMENTS. INFORMATION ON FALSE ALARMS WAS OBTAINED FROM POLICE REPORTS AND FROM INTERVIEWS WITH ALARM USERS AND ALARM MONITORING SERVICES. CAUSES OF FALSE ALARMS ARE PREDOMINANTLY ASSOCIATED WITH EQUIPMENT MALFUNCTION OR USER ERROR. IN ASSESSING THE DEGREE OF PROTECTION AFFORDED BY AN ALARM SYSTEM, THE STUDY EXAMINED THE RATE OF CRIMINAL ATTACK ON ALARMED PREMISES, DIFFERENCES IN DOLLAR COSTS BETWEEN ALARMED AND NON-ALARMED PREMISES, AND THE ARREST RATE FOR CRIMES COMMITTED ON ALARMED PREMISES. IT CONCLUDED THAT ALARM INSTALLATIONS DID NOT SEEM TO DETER CRIMINAL ATTACK, ALTHOUGH THEY DID CONTRIBUTE TO APPREHENSION OF THE CRIMINAL AFTER THE CRIME OCCURRED. IN ADDITION TO DETAILED TABLES ACCOMPANYING THE TEXT, THE APPENDIXES INCLUDE THE INTERVIEW FORM FOR ALARM USERS ON FALSE ALARMS AND ARREST DATA SORTED BY AREA, ALARM TYPE, MONITOR, AND VICTIMIZATION. (MJM)