FOUR WEEKS OF INTENSIVE FLIGHT TESTING OF THE STOL AND HELICOPTER IN REGULAR POLICE SERVICE WERE USED TO COLLECT THE BASIC OPERATIONS DATA. BOTH AIRCRAFT DEMONSTRATED HIGH LEVELS OF EFFECTIVENESS (FOR WHICH THE AVIATION SECTION WAS COMMENDED BY THE DIRECTOR OF PUBLIC SAFETY). THEIR MOST NOTABLE SUCCESSES WERE IN PROVIDING ILLUMINATION WHERE AND WHEN NEEDED, MAINTAINING SURVEILLANCE OVER CROWD MOVEMENTS AND CURFEW VIOLATORS, PURSUING FUGITIVES, DETECTING FIREBOMBINGS AND LOOTINGS IN PROGRESS, ASSISTING IN THE COMMAND AND CONTROL FUNCTIONS, AND LEADING DIRECTLY TO SEVERAL APPREHENSIONS. FOR JUNE AND JULY, 1970, THE STOL COST $16.99/FLIGHT HOUR IN FIXED AND DIRECT EXPENSES; DURING JANUARY JULY, 1970, THE HELICOPTER COST $28.94/FLIGHT HOUR FOR THE SAME EXPENSES. NOT ONLY WAS THE TOTAL COST/HOUR LESS FOR THE STOL THAN THE HELICOPTER, BUT SO WERE THE DIRECT OPERATING COSTS. HOWEVER, SINCE MORE DISCOVERIES AND APPREHENSIONS WERE MADE BY THE HELICOPTER, DURING FEWER FLIGHT HOURS, ITS COSTS (TOTAL OR DIRECT) WERE LESS PER DISCOVERY AND APPREHENSION THAN FOR THE STOL. THUS, IN THE PRESENT CASE, THE HELICOPTER APPEARS TO BE MORE COST/ EFFECTIVE. FURTHER, ON AN ANNUAL BASIS, THE STOL COSTS MORE THAN THE HELICOPTER FOR BOTH DIRECT AND TOTAL COSTS. (AUTHOR ABSTRACT)