One chapter describes the research design, sampling plans, and field procedures used in both the in-school surveys of the 8th, 10th, and 12th grade students and the follow-up surveys of young adults. Related methodological issues, such as response rates, population coverage, and the validity of the measures are also discussed. The study found that by the end of the eighth grade, more than a third (38 percent) of American secondary school students have tried an illicit drug, if inhalants are included as an illicit drug. Nearly half of all 10th graders have done so (46 percent), and just over half of 12th graders (52 percent). Three out of 10 young Americans have tried cocaine (29 percent in 1995) by the age of 30, and 6 percent have tried it by their senior year of high school. One in every 33 seniors (3 percent) have tried the particularly dangerous form of cocaine called crack; in the young adult sample, 1 in 26 have tried it. Approximately 1 in 22 (4.6 percent) high school seniors in 1995 smoked marijuana daily. Some 30 percent of seniors had consumed five or more drinks in a row at least once in the 2 weeks prior to the survey. One-third (34 percent) of seniors in 1995 were current cigarette smokers, and 22 percent already were current daily smokers; these numbers are increasing among seniors, as well as among the younger students; many of the lighter smokers will convert to heavy smoking after they leave high school. Despite the improvements between 1979 and 1991, this Nation's secondary school students and young adults show a level of involvement with illicit drugs that is greater than has been documented in any other industrialized nation in the world. 79 tables