The information came from nationally representative samples of 17,300 students in 8th grade, 13,900 students in 10th grade, and 14,100 students in 12th grade in public and private secondary schools. Students completed the self-report questionnaires, usually in their classrooms during a regular class period. Overall illicit drug use among teenagers remained steady in 1999 in all 3 grades after 1 or 2 years of deadline. The use of marijuana, amphetamines, hallucinogens, tranquilizers, heroin, and alcohol remained steady. The most important increases in use occurred in MDMA (ecstasy) among older students and in steroid use among younger adolescent males. The use of inhalants, Rohypnol, crack, crystal methamphetamine (ice) declined for some age groups. Thirty-five percent of 12th graders were current smokers, and 62 percent of 12th graders reported having been drunk on alcohol at least once. Findings indicated that the determinants of juvenile drug use are often specific to the drugs, that these determinants include both the perceived benefits and the perceived risks that young people come to associate with each drug, and that prevention must occur drug by drug to a considerable degree. Findings also indicated the continuous flow of new drugs introduced onto the drug scene or being rediscovered by young people. Figures and tables