The National Survey on Drug Use and Health (NSDUH) is the primary source of statistical information on the use of illegal drugs by the United States population. NSDUH collects data from the civilian, non-institutionalized population of the United States aged 12 years old or older. This overview report is intended to provide a concise summary of the key results from the 2004 NSDUH. It contains a subset of the results provided in the full report. Results are presented in separate chapters which discuss the national findings on seven topics: (1) use of illicit drugs; (2) use of alcohol; (3) use of tobacco products; (4) trends in initiation of substance use; (5) prevention-related issues; (6) substance dependence, abuse, and treatment; and (7) mental health. In addition, trends are presented and discussed. Highlighted findings include: (1) in 2004, 19.1 million Americans (7.9 percent) of the population aged 12 or older were current illicit drug users; (2) there were significant increases in the lifetime prevalence of use from 2003 to 2004 in several categories of pain relievers among those aged 18 to 25; (3) 121 million Americans (50.3 percent) aged 12 or older were current drinkers of alcohol in 2004; (4) 70.3 million Americans were current users of a tobacco product in 2004; (5) the 2002 NSDUH shows that the illicit drug category with the largest number of new users was non-medical use of pain relievers; (6) the percentage of youths aged 12 to 17 indicating that smoking marijuana once a month was a great risk increased from 32.4 percent in 2002 to 34.9 percent in 2003, but did not change between 2003 and 2004; and (7) 22.5 million Americans aged 12 or older in 2004 were classified with past year substance dependence or abuse. Figures, tables, and appendix