The data included youths entering the Youth Support Project during its first year, who completed Year 2 (Time 2) interviews, and who provided a Time 2 hair sample, and, in most cases, a voluntary urine sample for analysis. The collected urine specimens were analyzed by the EMIT process probing for the presence of six drugs: cannabinoids (THC), cocaine, barbiturates, opiates, PCP, and amphetamines. The hair specimen collection protocol involved collecting about half an inch of hair across the finger and cutting these strands as close to the scalp as possible. Most youths were male and averaged 14 years of age. The results were consistent with previous research. A large proportion of the youths in the study were marijuana users, and a smaller proportion, cocaine users. Drug testing indicated much higher rates of drug use, compared to self-reports (particularly where cocaine was concerned). The youths were more willing to report the use of marijuana than cocaine. Results also indicated that hair testing for drug use was a valuable tool for identifying recent drug use and treatment need among arrested youths--particularly cocaine. The picture of drug use provided by urinalysis may be too limited for treatment need estimation and planning purposes. The need for treatment for cocaine use would have gone virtually unidentified if practitioners relied solely on the urine test results of this study, with its 4 day surveillance window. If the findings continue to be supported, serious consideration should be given to using hair analysis for identifying recent drug use among arrested youths, rather than the more limited surveillance window for urine tests. 8 tables, 32 references, appendix