Risk factors included those individual characteristics or social environments associated with an increased likelihood of substance use, and protective factors were related to the decreased likelihood of substance use or nonuse. Analyses reported here are from 7,844 respondents aged 12 to 17 who represented the national population of 22 million in that age group. The first chapter describes the NHSDA methodology and the prevention risk and protective factors included in the survey. Chapter 2 examines the estimated prevalence of the various risk and protective factors in the U.S. population and how these vary by race/ethnicity, gender, and age. Chapter 3 examines the relationship of these factors to various levels of substance use. The focus was on marijuana; however, cigarette use, alcohol use, and the use of any were discussed as well. That chapter also considers the relative "odds" of using a substance for different levels of risk. Chapter 4 introduces multivariate techniques to analyze the strength of association of each of the major domains of risk and protective factors and of demographic variables with youth substance use. The classification approach used in this report combines factors into one of five domains: community, family, peer/individual, school, and general. A striking result of these analyses was the uniformity, regardless of the substance, in the patterns of association between substance use and risk and protective factors. Detailed data tables are presented in one appendix, and standard errors for selected tables are provided in another appendix. Also appended are distributions of risk and protective factors and substance use by age, along with further analyses of unexpected findings on the relationship of marijuana use to exposure to prevention messages. 24 figures, 13 tables, and 9 references