Survey data were collected during the spring of each year in approximately 125 to 145 public and private high schools selected to provide an accurate and representative cross-section of high school students throughout the coterminous United States. The survey employed multistage random sampling procedures and questionnaires. Nearly 4 in every 10 students in the 8th grade (38 percent) had tried an illicit drug and that 56 percent of students in the 12th grade had tried an illicit drug. In 1997, marijuana use leveled for 8th graders and decreased for 10th and 12th graders. Among seniors, the proportion using any illicit drug other than marijuana in the past year rose to 21 percent in 1997, from a low of 15 percent in 1992. The use of prescription-controlled stimulants increased by about half among 8th and 10th graders between 1991 and 1996. Among seniors, the prevalence of crack use leveled in 1987 at relatively low prevalence rates (3.9 percent). Among 8th and 10th graders, crack use rose gradually in the early 1990s, from 0.7 percent in 1991 to 1.8 percent by 1996 among 8th graders and from 0.9 percent in 1992 to 2.1 percent in 1996 among 10th graders. Cocaine use began to decline a year earlier than crack use, while PCP use fell sharply among seniors between 1979 and 1982 and reached a low point in 1988. The prevalence of heroin use among seniors fell by half between 1975 and 1979 and then stabilized until 1994 before rising significantly in 1995. Alcohol had been tried by 54 percent of 8th graders, 72 percent of 10th graders, and 82 percent of 12th graders, and active alcohol use was widespread. Alcohol use did not increase as the use of other illicit drugs decreased among seniors from the late 1970s to the early 1990s. Between 1975 and 1997, cigarettes were the most widely used of all drugs on a daily basis by high school students. Through the 1990-1997 period, there was a clear and continuing increase in cigarette smoking among teenagers. Data on the use of other drugs are also provided, including opiates, tranquilizers, and methaqualone, and male-female and racial differences in illicit drug use are noted. Health implications of heavy drinking, illicit drug use, and cigarette smoking are discussed. Attitudes and beliefs of young people about drug use and the social milieu of drug use are considered, as well as the link between drug use and school dropout. Supplemental data on survey procedures and findings are appended. Tables and figures