NSDUH, formerly known as the National Household Survey on Drug Abuse, is an annual survey of the civilian, noninstitutionalized population of the United States aged 12 years and older. Major research questions addressed by the report include the characteristics of adults with SMI; the characteristics of adults with SMI who use illicit drugs; and characteristics of adults with SMI who received mental health treatment in the past year. Following the introduction in chapter 1, chapter 2 describes the measures and statistical methods employed for the NSDUH. This report draws on data on adults aged 18 years or older from the 2002 survey; NSDUH interview data are gathered via computer-assisted interviewing to increase confidentiality and level of honest reporting. Chapter 3 offers findings on the prevalence and correlates of SMI among adults. During the 12 months prior to the NSDUH interview, 17.5 million adult respondents aged 18 or older reported experiences with SMI, representing 8.3 percent of all adults in the United States. Adults with SMI were more likely to be unemployed than were adults without SMI. During 2002, there were 4.0 million individuals with SMI and a substance use disorder, representing 12.2 percent of adults aged 18 or older. Chapter 4 describes findings regarding the prevalence of mental health treatment and substance use treatment among adults with SMI and a substance use disorder. An estimated 48 percent of the 17.5 million adults with SMI received treatment during the 12 months prior to the interview. However, of these 48 percent who received treatment, only 11.8 percent received treatment for both SMI and substance use disorder. Chapter 5 presents a summary and conclusions. Figures, tables, references, appendix