THE ESSAYS CONTAINED IN THE MONOGRAPH ARE BASED ON RECOMMENDATIONS MADE TO AUTHORS RESULTING FROM MEETINGS HELD BY THE SPECIAL ACTION OFFICE FOR DRUG ABUSE PREVENTION. THE MEETINGS WERE HELD TO REVIEW HOW TERMS AND CONCEPTS WERE BEING DEFINED AND OPERATIONALIZED IN DRUG USE RESEARCH AND TO HELP CLARIFY THESE TERMS. RESULTING ESSAYS DISCUSS THE FOLLOWING: THE HISTORY OF DRUG USE; MEASURES OF CURRENCY OR REGENCY, 'EVER USE,' AND 'FREQUENCY-QUANTITY' IN DRUG USE SURVEYS; CONDITIONS OF DRUG USE; EFFECTS OF DRUG USE; AND SOME WARNINGS CONCERNING SUBJECTIVE CONCEPTS INVOLVING TRYING, MAINTAINING, OR CHANGING USE AND REASONS FOR USE AND NONUSE. OTHER ESSAYS OFFER DEFINITIONS OF ADDICTION LIABILITY ASSOCIATED WITH DIFFERENT PATTERNS OF DRUG USE AND OF POLYDRUG USE. A FUNCTIONAL TAXONOMY OF DRUGS IS INCLUDED, AND APPENDIXES CONTAIN OPERATIONAL DEFINITIONS USED IN RECENT SOCIOECONOMIC RESEARCH ON DRUGS AND EXAMPLES OF QUESTIONNAIRES. (KJM)