The questionnaires were completed by 21,238 students, of whom 91.9 percent attended public schools. Results revealed that almost one-fourth of 10th graders were using marijuana; more than half of these were doing so once a week or more often. Approximately 10 percent were using amphetamines; the same proportion were using barbiturates. Heroin use was reported by 2.5 percent. The percentage of drug users tended to be somewhat higher for urbanized counties than for rural areas, although each school and each county appeared to have substantial numbers of drug abusers among their youth on the basis of these data. The current users of each drug reported having more available spending money than nonusers of that drugs. Current users were also more knowledgeable than nonusers regarding both street and technical terms related to drugs. Overall, about 25 percent of the students were currently abusing at least one drug other than alcohol or tobacco. Tables and 10 references