Highlights of survey findings include: (1) in 2008, an estimated 20.1 million Americans aged 12 or older were current (past month) illicit drug users, representing 8.0 percent of the population aged 12 years old or older; (2) from 2002 to 2008, there was an increase among young adults aged 18 to 25 in the rate of current nonmedical use of prescription pain relievers (from 4.1 to 4.6 percent) and in LSD (from 0.1 to 0.3 percent); (3) in 2008, 10.0 million persons aged 12 or older reported driving under the influence of illicit drugs during the past year; (4) slightly more than half of Americans aged 12 or older reported being current drinkers of alcohol (51.6 percent); (5) the rate of past month cigarette use among 12 to 17 year olds declined from 9.8 percent in 2007 to 9.1 percent in 2008, continuing a decline since 2002 when the rate was 13.0 percent; (6) following substantial drops in initiation between 2002 and 2003, estimates of initiation of Ecstasy and LSD among persons aged 12 or older have increased significantly; between 2003 and 2008, the number of Ecstasy initiates increased from 642,000 to 894,000, and the number of LSD initiates increased from 200,000 to 394,000; (7) between 2002 and 2008, there was no change in the number of persons with substance dependence or abuse (22.0 million in 2002 and 22.2 million in 2008); and (8) rates of serious mental illness (SMI) in 2008 were highest for adults aged 18 to 25 (7.4 percent) and lowest for adults aged 50 or older (2.3 percent). Results are presented from the 2008 National Survey on Drug Use and Health (NSDUH). It presents national estimates and trends on rates of use, numbers of users, and other measures related to illicit drugs, alcohol, and tobacco products. Tables, figures, and appendixes A-H