ALTHOUGH FEW INFORMANTS ARE COMPLETELY RELIABLE AND TRUSTWORTHY, MOST CAN SUPPLY INDISPENSABLE LEADS IN SUCH FIELDS AS VICE, NARCOTICS, AND GAMBLING. INFORMANTS FALL INTO THE FOLLOWING CATEGORIES (WITH SOME OVERLAPPING): (1) SNOOPERS, PEOPLE WITH AN INSATIABLE CURIOSITY ABOUT OTHER PEOPLE'S BUSINESS; (2) PEOPLE WITH SPECIAL OPPORTUNITIES TO COLLECT INFORMATION; (3) 'INVISIBLE' PEOPLE, WORKERS WHO SEEM TO BE PART OF THEIR SURROUNDINGS AND ARE UNNOTICED; (4) PROFESSIONAL LISTENERS, SUCH AS BARTENDERS AND WAITRESSES; (5) FRINGE OPERATORS, SUCH AS DRUG ADDICTS AND PROSTITUTES; AND (6) MINOR CRIMINALS. MOTIVES FOR INFORMING INCLUDE FINANCIAL GAIN, FEAR, HOSTILITY, OBLIGATION, DESIRE FOR ATTENTION, AND CRIMINAL INTENT. OFFICERS' ABILITY TO CULTIVATE INFORMANTS DEPENDS ON THEIR REPUTATION FOR FAIRNESS AND HONESTY IN THE COMMUNITY, THEIR SCOUTING PROSPECTS, AND THEIR RAPPORT WITH POTENTIAL INFORMANTS. INVESTIGATORS SHOULD NEVER MAKE PROMISES TO INFORMANTS THAT CANNOT BE KEPT, SHOULD USE THE INFORMANTS' LANGUAGE SO AS TO BE UNDERSTOOD, SHOULD AVOID ANY SOCIAL CONTACT OR EMOTIONAL INVOLVEMENT WITH INFORMANTS, SHOULD SHOW GRATITUDE TO THE INFORMANT, AND SHOULD USE AN UNLISTED NUMBER. METHODS OF HANDLING HOSTILE INFORMANTS AND SAFEGUARDING THEIR ANONYMITY ARE NOTED. AN INSTRUCTOR'S GUIDE AND STUDY NOTES ARE INCLUDED. (WJR)