A PASSIVE ELECTRONIC TAG (PET) SYSTEM HAS BEEN DEVELOPED BY THE ADVANCED TECHNOLOGY DIVISION OF THE DRUG ENFORCEMENT ADMINISTRATION. THE PURPOSE OF THE PET SYSTEM IS TO IDENTIFY COVERTLY TAGGED AUTOMOBILES AND BOATS AS THEY TRAVEL IN THE PROXIMITY OF THE SYSTEM INTERROGATOR. EVALUATION OF THE PLACES, TIMES, AND CONDITIONS WHERE SUCH OPERATIONS HAVE PROVEN VALUABLE LED TO THE FOLLOWING PERFORMANCE REQUIREMENTS FOR THE TAG: (1) COVERT--SMALL, EASILY CONCEALED; (2) PASSIVE--NO POWER DRAIN FROM THE VEHICLE OR BATTERIES; (3) MOUNTING--QUICKLY AND EASILY ATTACHED UNDER ADVERSE CIRCUMSTANCES; (4) SPECIFICITY--EACH TAG HAS A UNIQUE IDENTITY; (5) TEMPERATURE RANGE--20 DEGREES F TO +160 DEGREES F; (6) DETECTION RANGE--50 TO 650 FEET. THE INTERROGATOR MUST BE UNOBTRUSIVE, PORTABLE, HAVE A REMOTE READOUT, AND BE ABLE TO OPERATE IN TEMPERATURES RANGING FROM 0 DEGREES FARENHEIT TO +140 DEGREES FARENHEIT. SYSTEM OPERATIONS THEORY IS EXPLAINED AND THE ENGINEERING MODEL DEVELOPMENT IS DISCUSSED. TEST RESULTS SHOW THAT A SHORE-BASED INTERROGATOR RELIABLY DETECTED AND IDENTIFIED TAGS MOUNTED IN THE INTERIOR OF A BOAT. HOWEVER, EXTERIOR TAGS DID NOT MEET THE RANGE SPECIFICATIONS AND THUS ARE NOT SUITABLE FOR THE MARINE ENVIRONMENT. LAND VEHICLE OPERATIONAL TESTS INDICATED THAT THE SYSTEM CAN BE USED IN ITS PRESENT STATE TO DETECT VEHICLES IN TOLL PLAZAS OR OTHER AREAS WHERE VEHICLES ARE CONSTRAINED TO LOWER SPEEDS. FIGURES AND TABLES WITH STATISTICAL DATA ARE PROVIDED. SEE ALSO NCJ 38864, 52569, 57707-57715, AND 57717-57726. (PRG)