Monitoring the Future is an ongoing program of research intended to assess the changing lifestyles, values, and preferences of American youth. This publication, from the occasional paper series, describes a study that monitors drug use and potential explanatory factors among American secondary school students, college students, and young adults. The study aims to monitor drug use and related factors in order to provide social indicators of historical change, to distinguish the three types of change (age, period, cohort), and to analyze results at both individual and aggregate levels. Eleven specific objectives of the study are described and each is explained, including its logic and rationale, relevant theory, literature cited, and progress. Objectives 1 through 3 concern drug use and potential explanatory factors; Objective 4 distinguishes which kinds of change are occurring for various types of drug use; Objectives 5 through 9 study the causes, consequences, and developmental patterns associated with types of change in drug use; and Objectives 10 and 11 list additional methodological, policy, data-sharing, and other objectives. (Contains over 500 references.) (JDM)